<?xml version="1.0" encoding="us-ascii"?>
<!--Generated by EDGARfilings PROfile 6.2.0.0 Broadridge-->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:t1="http://xbrl.org/2005/xbrldt">
  <link:roleRef roleURI="http://mineralstech.com/role/ScheduleIivaluationAndQualifyingAccountsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#ScheduleIivaluationAndQualifyingAccountsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/QuarterlyFinancialDataUnauditedDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#QuarterlyFinancialDataUnauditedDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/SegmentAndRelatedInformationSalesByProductCategoryDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#SegmentAndRelatedInformationSalesByProductCategoryDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/SegmentAndRelatedInformationSalesByRegionCategoryDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#SegmentAndRelatedInformationSalesByRegionCategoryDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/SegmentAndRelatedInformationReportableSegmentsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#SegmentAndRelatedInformationReportableSegmentsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccountingForAssetRetirementObligationsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccountingForAssetRetirementObligationsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccumulatedOtherComprehensiveIncomeLossDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockholdersEquityStockAwardAndIncentivePlanDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockholdersEquityStockAwardAndIncentivePlanDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockholdersEquityCapitalStockAndCashDividendsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockholdersEquityCapitalStockAndCashDividendsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/LitigationDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#LitigationDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansSavingsAndInvestmentPlansDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansSavingsAndInvestmentPlansDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansInvestmentStrategiesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansInvestmentStrategiesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansEstimatedFutureBenefitPaymentsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansEstimatedFutureBenefitPaymentsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansContributionsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansContributionsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansReconciliationOfChangesInFairValueMeasurementOfPlanAssetsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansReconciliationOfChangesInFairValueMeasurementOfPlanAssetsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansDomesticAndForeignPensionPlanAssetsAndSummaryOfDefinedBenefitPensionPlanAssetsMeasuredAtFairValueDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansDomesticAndForeignPensionPlanAssetsAndSummaryOfDefinedBenefitPensionPlanAssetsMeasuredAtFairValueDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansFairValuesByAssetCategoryDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansFairValuesByAssetCategoryDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansWeightedAverageAssetAllocationByAssetCategoryDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansWeightedAverageAssetAllocationByAssetCategoryDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansWeightedAverageAssumptionsUsedDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansWeightedAverageAssumptionsUsedDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansEstimatedAmortizationOfAmountsInOtherAccumulatedComprehensiveIncomeDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansEstimatedAmortizationOfAmountsInOtherAccumulatedComprehensiveIncomeDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansComponentsOfNetPeriodicBenefitCostsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansComponentsOfNetPeriodicBenefitCostsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansChangesInPlanAssetsAndBenefitObligationsRecognizedInOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansChangesInPlanAssetsAndBenefitObligationsRecognizedInOtherComprehensiveIncomeDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansAmountsRecognizedInAccumulatedOtherComprehensiveIncomeNetOfRelatedTaxEffectsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansAmountsRecognizedInAccumulatedOtherComprehensiveIncomeNetOfRelatedTaxEffectsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansAmountsRecognizedInConsolidatedBalanceSheetDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansAmountsRecognizedInConsolidatedBalanceSheetDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansPensionObligationAndFundedStatusDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansPensionObligationAndFundedStatusDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/LongtermDebtAndCommitmentsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#LongtermDebtAndCommitmentsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/FinancialInstrumentsAndConcentrationsOfCreditRiskDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#FinancialInstrumentsAndConcentrationsOfCreditRiskDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/FairValueOfFinancialInstrumentsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#FairValueOfFinancialInstrumentsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#DerivativeFinancialInstrumentsAndHedgingActivitiesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsAcquiredIntangibleAssetsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#GoodwillAndOtherIntangibleAssetsAcquiredIntangibleAssetsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#GoodwillAndOtherIntangibleAssetsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/PropertyPlantAndEquipmentDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#PropertyPlantAndEquipmentDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/InventoriesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#InventoriesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/IncomeTaxesDetailsCalc01" xlink:type="simple" xlink:href="mtx-20191231.xsd#IncomeTaxesDetailsCalc01" />
  <link:roleRef roleURI="http://mineralstech.com/role/IncomeTaxesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#IncomeTaxesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/EarningsPerShareEpsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#EarningsPerShareEpsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockbasedCompensationRestrictedStockDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockbasedCompensationRestrictedStockDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockbasedCompensationStockAwardAndIncentivePlanAndStockOptionsDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockbasedCompensationStockAwardAndIncentivePlanAndStockOptionsDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/RestructuringAndOtherItemsNetDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#RestructuringAndOtherItemsNetDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/BusinessCombinationDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#BusinessCombinationDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/RevenueFromContractsWithCustomersDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#RevenueFromContractsWithCustomersDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/LeasesDetailsCalc01" xlink:type="simple" xlink:href="mtx-20191231.xsd#LeasesDetailsCalc01" />
  <link:roleRef roleURI="http://mineralstech.com/role/LeasesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#LeasesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/SummaryOfSignificantAccountingPoliciesDetails" xlink:type="simple" xlink:href="mtx-20191231.xsd#SummaryOfSignificantAccountingPoliciesDetails" />
  <link:roleRef roleURI="http://mineralstech.com/role/QuarterlyFinancialDataUnauditedTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#QuarterlyFinancialDataUnauditedTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/SegmentAndRelatedInformationTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#SegmentAndRelatedInformationTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccountingForAssetRetirementObligationsTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccountingForAssetRetirementObligationsTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLossTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccumulatedOtherComprehensiveIncomeLossTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockholdersEquityTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockholdersEquityTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlansTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlansTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/LongtermDebtAndCommitmentsTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#LongtermDebtAndCommitmentsTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/FairValueOfFinancialInstrumentsTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#FairValueOfFinancialInstrumentsTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#GoodwillAndOtherIntangibleAssetsTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/PropertyPlantAndEquipmentTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#PropertyPlantAndEquipmentTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/InventoriesTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#InventoriesTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/IncomeTaxesTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#IncomeTaxesTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/EarningsPerShareEpsTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#EarningsPerShareEpsTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockbasedCompensationTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockbasedCompensationTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/RestructuringAndOtherItemsNetTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#RestructuringAndOtherItemsNetTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/BusinessCombinationTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#BusinessCombinationTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/RevenueFromContractsWithCustomersTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#RevenueFromContractsWithCustomersTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/LeasesTables" xlink:type="simple" xlink:href="mtx-20191231.xsd#LeasesTables" />
  <link:roleRef roleURI="http://mineralstech.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" xlink:href="mtx-20191231.xsd#SummaryOfSignificantAccountingPoliciesPolicies" />
  <link:roleRef roleURI="http://mineralstech.com/role/ScheduleIivaluationAndQualifyingAccounts" xlink:type="simple" xlink:href="mtx-20191231.xsd#ScheduleIivaluationAndQualifyingAccounts" />
  <link:roleRef roleURI="http://mineralstech.com/role/QuarterlyFinancialDataUnaudited" xlink:type="simple" xlink:href="mtx-20191231.xsd#QuarterlyFinancialDataUnaudited" />
  <link:roleRef roleURI="http://mineralstech.com/role/SegmentAndRelatedInformation" xlink:type="simple" xlink:href="mtx-20191231.xsd#SegmentAndRelatedInformation" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccountingForAssetRetirementObligations" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccountingForAssetRetirementObligations" />
  <link:roleRef roleURI="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLoss" xlink:type="simple" xlink:href="mtx-20191231.xsd#AccumulatedOtherComprehensiveIncomeLoss" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockholdersEquity" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockholdersEquity" />
  <link:roleRef roleURI="http://mineralstech.com/role/Litigation" xlink:type="simple" xlink:href="mtx-20191231.xsd#Litigation" />
  <link:roleRef roleURI="http://mineralstech.com/role/BenefitPlans" xlink:type="simple" xlink:href="mtx-20191231.xsd#BenefitPlans" />
  <link:roleRef roleURI="http://mineralstech.com/role/LongtermDebtAndCommitments" xlink:type="simple" xlink:href="mtx-20191231.xsd#LongtermDebtAndCommitments" />
  <link:roleRef roleURI="http://mineralstech.com/role/FinancialInstrumentsAndConcentrationsOfCreditRisk" xlink:type="simple" xlink:href="mtx-20191231.xsd#FinancialInstrumentsAndConcentrationsOfCreditRisk" />
  <link:roleRef roleURI="http://mineralstech.com/role/FairValueOfFinancialInstruments" xlink:type="simple" xlink:href="mtx-20191231.xsd#FairValueOfFinancialInstruments" />
  <link:roleRef roleURI="http://mineralstech.com/role/DerivativeFinancialInstrumentsAndHedgingActivities" xlink:type="simple" xlink:href="mtx-20191231.xsd#DerivativeFinancialInstrumentsAndHedgingActivities" />
  <link:roleRef roleURI="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssets" xlink:type="simple" xlink:href="mtx-20191231.xsd#GoodwillAndOtherIntangibleAssets" />
  <link:roleRef roleURI="http://mineralstech.com/role/PropertyPlantAndEquipment" xlink:type="simple" xlink:href="mtx-20191231.xsd#PropertyPlantAndEquipment" />
  <link:roleRef roleURI="http://mineralstech.com/role/Inventories" xlink:type="simple" xlink:href="mtx-20191231.xsd#Inventories" />
  <link:roleRef roleURI="http://mineralstech.com/role/IncomeTaxes" xlink:type="simple" xlink:href="mtx-20191231.xsd#IncomeTaxes" />
  <link:roleRef roleURI="http://mineralstech.com/role/EarningsPerShareEps" xlink:type="simple" xlink:href="mtx-20191231.xsd#EarningsPerShareEps" />
  <link:roleRef roleURI="http://mineralstech.com/role/StockbasedCompensation" xlink:type="simple" xlink:href="mtx-20191231.xsd#StockbasedCompensation" />
  <link:roleRef roleURI="http://mineralstech.com/role/RestructuringAndOtherItemsNet" xlink:type="simple" xlink:href="mtx-20191231.xsd#RestructuringAndOtherItemsNet" />
  <link:roleRef roleURI="http://mineralstech.com/role/BusinessCombination" xlink:type="simple" xlink:href="mtx-20191231.xsd#BusinessCombination" />
  <link:roleRef roleURI="http://mineralstech.com/role/RevenueFromContractsWithCustomers" xlink:type="simple" xlink:href="mtx-20191231.xsd#RevenueFromContractsWithCustomers" />
  <link:roleRef roleURI="http://mineralstech.com/role/Leases" xlink:type="simple" xlink:href="mtx-20191231.xsd#Leases" />
  <link:roleRef roleURI="http://mineralstech.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="simple" xlink:href="mtx-20191231.xsd#SummaryOfSignificantAccountingPolicies" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedStatementsOfChangesInShareholdersEquity" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedStatementsOfChangesInShareholdersEquity" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedStatementsOfCashFlows" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedStatementsOfComprehensiveIncome" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedStatementsOfIncome" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedStatementsOfIncome" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedBalanceSheetsParenthetical" />
  <link:roleRef roleURI="http://mineralstech.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="mtx-20191231.xsd#ConsolidatedBalanceSheets" />
  <link:roleRef roleURI="http://mineralstech.com/role/DocumentAndEntityInformation" xlink:type="simple" xlink:href="mtx-20191231.xsd#DocumentAndEntityInformation" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/DocumentAndEntityInformation" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedBalanceSheets" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedBalanceSheetsParenthetical" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedStatementsOfIncome">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="StatementLineItems" xlink:title="StatementLineItems" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_StatementOfIncomeAbstract" xlink:label="StatementOfIncomeAbstract" xlink:title="StatementOfIncomeAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="StatementOfIncomeAbstract" xlink:title="definition: StatementLineItems to StatementOfIncomeAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: StatementLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="CostOfGoodsAndServicesSold" xlink:title="CostOfGoodsAndServicesSold" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="CostOfGoodsAndServicesSold" xlink:title="definition: StatementLineItems to CostOfGoodsAndServicesSold" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GrossProfit" xlink:label="GrossProfit" xlink:title="GrossProfit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="GrossProfit" xlink:title="definition: StatementLineItems to GrossProfit" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="SellingGeneralAndAdministrativeExpense" xlink:title="SellingGeneralAndAdministrativeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="SellingGeneralAndAdministrativeExpense" xlink:title="definition: StatementLineItems to SellingGeneralAndAdministrativeExpense" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="ResearchAndDevelopmentExpense" xlink:title="ResearchAndDevelopmentExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="ResearchAndDevelopmentExpense" xlink:title="definition: StatementLineItems to ResearchAndDevelopmentExpense" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="BusinessCombinationAcquisitionRelatedCosts" xlink:title="BusinessCombinationAcquisitionRelatedCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="BusinessCombinationAcquisitionRelatedCosts" xlink:title="definition: StatementLineItems to BusinessCombinationAcquisitionRelatedCosts" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LitigationSettlementExpense" xlink:label="LitigationSettlementExpense" xlink:title="LitigationSettlementExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="LitigationSettlementExpense" xlink:title="definition: StatementLineItems to LitigationSettlementExpense" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="RestructuringCharges" xlink:title="RestructuringCharges" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="RestructuringCharges" xlink:title="definition: StatementLineItems to RestructuringCharges" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="OperatingIncomeLoss" xlink:title="OperatingIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="OperatingIncomeLoss" xlink:title="definition: StatementLineItems to OperatingIncomeLoss" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense" xlink:label="InterestExpense" xlink:title="InterestExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="InterestExpense" xlink:title="definition: StatementLineItems to InterestExpense" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DebtModificationCostsAndFees" xlink:label="DebtModificationCostsAndFees" xlink:title="DebtModificationCostsAndFees" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="DebtModificationCostsAndFees" xlink:title="definition: StatementLineItems to DebtModificationCostsAndFees" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NonCashPensionSettlementCosts" xlink:label="NonCashPensionSettlementCosts" xlink:title="NonCashPensionSettlementCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="NonCashPensionSettlementCosts" xlink:title="definition: StatementLineItems to NonCashPensionSettlementCosts" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="OtherNonoperatingIncomeExpense" xlink:title="OtherNonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="OtherNonoperatingIncomeExpense" xlink:title="definition: StatementLineItems to OtherNonoperatingIncomeExpense" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="NonoperatingIncomeExpense" xlink:title="NonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="NonoperatingIncomeExpense" xlink:title="definition: StatementLineItems to NonoperatingIncomeExpense" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="definition: StatementLineItems to IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="IncomeTaxExpenseBenefit" xlink:title="IncomeTaxExpenseBenefit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="IncomeTaxExpenseBenefit" xlink:title="definition: StatementLineItems to IncomeTaxExpenseBenefit" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromEquityMethodInvestments" xlink:label="IncomeLossFromEquityMethodInvestments" xlink:title="IncomeLossFromEquityMethodInvestments" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="IncomeLossFromEquityMethodInvestments" xlink:title="definition: StatementLineItems to IncomeLossFromEquityMethodInvestments" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="ProfitLoss" xlink:title="ProfitLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="ProfitLoss" xlink:title="definition: StatementLineItems to ProfitLoss" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="NetIncomeLossAttributableToNoncontrollingInterest" xlink:title="NetIncomeLossAttributableToNoncontrollingInterest" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="NetIncomeLossAttributableToNoncontrollingInterest" xlink:title="definition: StatementLineItems to NetIncomeLossAttributableToNoncontrollingInterest" order="20.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="NetIncomeLoss" xlink:title="NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="NetIncomeLoss" xlink:title="definition: StatementLineItems to NetIncomeLoss" order="21.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedAbstract" xlink:label="EarningsPerShareBasicAndDilutedAbstract" xlink:title="EarningsPerShareBasicAndDilutedAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareBasicAndDilutedAbstract" xlink:title="definition: StatementLineItems to EarningsPerShareBasicAndDilutedAbstract" order="22.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared" xlink:label="CommonStockDividendsPerShareDeclared" xlink:title="CommonStockDividendsPerShareDeclared" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="CommonStockDividendsPerShareDeclared" xlink:title="definition: StatementLineItems to CommonStockDividendsPerShareDeclared" order="23.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:label="EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:title="EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" xlink:title="definition: StatementLineItems to EarningsPerShareBasicAndDilutedOtherDisclosuresAbstract" order="24.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="WeightedAverageNumberOfSharesOutstandingBasic" xlink:title="WeightedAverageNumberOfSharesOutstandingBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="WeightedAverageNumberOfSharesOutstandingBasic" xlink:title="definition: StatementLineItems to WeightedAverageNumberOfSharesOutstandingBasic" order="25.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="WeightedAverageNumberOfDilutedSharesOutstanding" xlink:title="WeightedAverageNumberOfDilutedSharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="WeightedAverageNumberOfDilutedSharesOutstanding" xlink:title="definition: StatementLineItems to WeightedAverageNumberOfDilutedSharesOutstanding" order="26.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="EarningsPerShareBasicAbstract" xlink:title="EarningsPerShareBasicAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareBasicAbstract" xlink:title="definition: StatementLineItems to EarningsPerShareBasicAbstract" order="27.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDilutedAbstract" xlink:label="EarningsPerShareDilutedAbstract" xlink:title="EarningsPerShareDilutedAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareDilutedAbstract" xlink:title="definition: StatementLineItems to EarningsPerShareDilutedAbstract" order="28.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="EarningsPerShareDiluted" xlink:title="EarningsPerShareDiluted" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareDiluted" xlink:title="definition: StatementLineItems to EarningsPerShareDiluted" order="29.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="EarningsPerShareBasic" xlink:title="EarningsPerShareBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="EarningsPerShareBasic" xlink:title="definition: StatementLineItems to EarningsPerShareBasic" order="30.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="StatementTable" xlink:title="StatementTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="StatementLineItems" xlink:to="StatementTable" xlink:title="definition: StatementLineItems to StatementTable" order="31.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="ProductOrServiceAxis" xlink:title="ProductOrServiceAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="StatementTable" xlink:to="ProductOrServiceAxis" xlink:title="definition: StatementTable to ProductOrServiceAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain_2" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain_2" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProductMember" xlink:label="ProductMember" xlink:title="ProductMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="ProductMember" xlink:title="definition: ProductsAndServicesDomain to ProductMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ServiceMember" xlink:label="ServiceMember" xlink:title="ServiceMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="ServiceMember" xlink:title="definition: ProductsAndServicesDomain to ServiceMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedStatementsOfComprehensiveIncome" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedStatementsOfCashFlows" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ConsolidatedStatementsOfChangesInShareholdersEquity">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="StatementLineItems" xlink:title="StatementLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:title="StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:title="definition: StatementLineItems to StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="ProfitLoss" xlink:title="ProfitLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="ProfitLoss" xlink:title="definition: StatementLineItems to ProfitLoss" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="OtherComprehensiveIncomeLossNetOfTax" xlink:title="OtherComprehensiveIncomeLossNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="OtherComprehensiveIncomeLossNetOfTax" xlink:title="definition: StatementLineItems to OtherComprehensiveIncomeLossNetOfTax" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Dividends" xlink:label="Dividends" xlink:title="Dividends" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="Dividends" xlink:title="definition: StatementLineItems to Dividends" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:title="MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:title="definition: StatementLineItems to MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions" xlink:label="MinorityInterestDecreaseFromRedemptions" xlink:title="MinorityInterestDecreaseFromRedemptions" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="MinorityInterestDecreaseFromRedemptions" xlink:title="definition: StatementLineItems to MinorityInterestDecreaseFromRedemptions" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:title="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:title="definition: StatementLineItems to CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:label="NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:title="NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:title="definition: StatementLineItems to NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationGross" xlink:label="StockIssuedDuringPeriodValueShareBasedCompensationGross" xlink:title="StockIssuedDuringPeriodValueShareBasedCompensationGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="StockIssuedDuringPeriodValueShareBasedCompensationGross" xlink:title="definition: StatementLineItems to StockIssuedDuringPeriodValueShareBasedCompensationGross" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:label="AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:title="AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" xlink:title="definition: StatementLineItems to AdjustmentsToAdditionalPaidInCapitalTaxEffectFromShareBasedCompensation" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="TreasuryStockValueAcquiredCostMethod" xlink:title="TreasuryStockValueAcquiredCostMethod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="TreasuryStockValueAcquiredCostMethod" xlink:title="definition: StatementLineItems to TreasuryStockValueAcquiredCostMethod" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:title="AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="StatementLineItems" xlink:to="AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:title="definition: StatementLineItems to AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="StatementTable" xlink:title="StatementTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="StatementLineItems" xlink:to="StatementTable" xlink:title="definition: StatementLineItems to StatementTable" order="13.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="StatementEquityComponentsAxis" xlink:title="StatementEquityComponentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="StatementTable" xlink:to="StatementEquityComponentsAxis" xlink:title="definition: StatementTable to StatementEquityComponentsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="EquityComponentDomain" xlink:title="EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementEquityComponentsAxis" xlink:to="EquityComponentDomain" xlink:title="definition: StatementEquityComponentsAxis to EquityComponentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="EquityComponentDomain_2" xlink:title="EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementEquityComponentsAxis" xlink:to="EquityComponentDomain_2" xlink:title="definition: StatementEquityComponentsAxis to EquityComponentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="CommonStockMember" xlink:title="CommonStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="CommonStockMember" xlink:title="definition: EquityComponentDomain to CommonStockMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="AdditionalPaidInCapitalMember" xlink:title="AdditionalPaidInCapitalMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="AdditionalPaidInCapitalMember" xlink:title="definition: EquityComponentDomain to AdditionalPaidInCapitalMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="RetainedEarningsMember" xlink:title="RetainedEarningsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="RetainedEarningsMember" xlink:title="definition: EquityComponentDomain to RetainedEarningsMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="AccumulatedOtherComprehensiveIncomeMember" xlink:title="AccumulatedOtherComprehensiveIncomeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="AccumulatedOtherComprehensiveIncomeMember" xlink:title="definition: EquityComponentDomain to AccumulatedOtherComprehensiveIncomeMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="TreasuryStockMember" xlink:title="TreasuryStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="TreasuryStockMember" xlink:title="definition: EquityComponentDomain to TreasuryStockMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="NoncontrollingInterestMember" xlink:title="NoncontrollingInterestMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="NoncontrollingInterestMember" xlink:title="definition: EquityComponentDomain to NoncontrollingInterestMember" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="AdjustmentsForNewAccountingPronouncementsAxis" xlink:title="AdjustmentsForNewAccountingPronouncementsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="StatementTable" xlink:to="AdjustmentsForNewAccountingPronouncementsAxis" xlink:title="definition: StatementTable to AdjustmentsForNewAccountingPronouncementsAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="TypeOfAdoptionMember" xlink:title="TypeOfAdoptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="TypeOfAdoptionMember" xlink:title="definition: AdjustmentsForNewAccountingPronouncementsAxis to TypeOfAdoptionMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="TypeOfAdoptionMember_2" xlink:title="TypeOfAdoptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="TypeOfAdoptionMember_2" xlink:title="definition: AdjustmentsForNewAccountingPronouncementsAxis to TypeOfAdoptionMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementMember" xlink:label="NewAccountingPronouncementMember" xlink:title="NewAccountingPronouncementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TypeOfAdoptionMember" xlink:to="NewAccountingPronouncementMember" xlink:title="definition: TypeOfAdoptionMember to NewAccountingPronouncementMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201802Member" xlink:label="AccountingStandardsUpdate201802Member" xlink:title="AccountingStandardsUpdate201802Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementMember" xlink:to="AccountingStandardsUpdate201802Member" xlink:title="definition: NewAccountingPronouncementMember to AccountingStandardsUpdate201802Member" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SummaryOfSignificantAccountingPolicies" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/Leases" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RevenueFromContractsWithCustomers" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BusinessCombination" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RestructuringAndOtherItemsNet" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockbasedCompensation" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/EarningsPerShareEps" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/IncomeTaxes" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/Inventories" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/PropertyPlantAndEquipment" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssets" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/DerivativeFinancialInstrumentsAndHedgingActivities" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/FairValueOfFinancialInstruments" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/FinancialInstrumentsAndConcentrationsOfCreditRisk" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LongtermDebtAndCommitments" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlans" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/Litigation" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockholdersEquity" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLoss" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccountingForAssetRetirementObligations" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SegmentAndRelatedInformation" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/QuarterlyFinancialDataUnaudited" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ScheduleIivaluationAndQualifyingAccounts" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SummaryOfSignificantAccountingPoliciesPolicies" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LeasesTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RevenueFromContractsWithCustomersTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BusinessCombinationTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RestructuringAndOtherItemsNetTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockbasedCompensationTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/EarningsPerShareEpsTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/IncomeTaxesTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/InventoriesTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/PropertyPlantAndEquipmentTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/FairValueOfFinancialInstrumentsTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LongtermDebtAndCommitmentsTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockholdersEquityTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLossTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccountingForAssetRetirementObligationsTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SegmentAndRelatedInformationTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/QuarterlyFinancialDataUnauditedTables" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SummaryOfSignificantAccountingPoliciesDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:label="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:title="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RecentlyAdoptedAccountingStandardsAbstract" xlink:label="RecentlyAdoptedAccountingStandardsAbstract" xlink:title="RecentlyAdoptedAccountingStandardsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="RecentlyAdoptedAccountingStandardsAbstract" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to RecentlyAdoptedAccountingStandardsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLossAbstract" xlink:label="OperatingIncomeLossAbstract" xlink:title="OperatingIncomeLossAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="OperatingIncomeLossAbstract" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to OperatingIncomeLossAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="SellingGeneralAndAdministrativeExpense" xlink:title="SellingGeneralAndAdministrativeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="SellingGeneralAndAdministrativeExpense" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to SellingGeneralAndAdministrativeExpense" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="OtherNonoperatingIncomeExpense" xlink:title="OtherNonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="OtherNonoperatingIncomeExpense" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to OtherNonoperatingIncomeExpense" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="OperatingLeaseLiabilityCurrent" xlink:title="OperatingLeaseLiabilityCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="OperatingLeaseLiabilityCurrent" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to OperatingLeaseLiabilityCurrent" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="OperatingLeaseRightOfUseAsset" xlink:title="OperatingLeaseRightOfUseAsset" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="OperatingLeaseRightOfUseAsset" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to OperatingLeaseRightOfUseAsset" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredCosts" xlink:label="DeferredCosts" xlink:title="DeferredCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="DeferredCosts" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to DeferredCosts" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:label="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:title="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:label="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:title="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:to="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems to NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" order="9.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="AdjustmentsForNewAccountingPronouncementsAxis" xlink:title="AdjustmentsForNewAccountingPronouncementsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:to="AdjustmentsForNewAccountingPronouncementsAxis" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleTable to AdjustmentsForNewAccountingPronouncementsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="TypeOfAdoptionMember" xlink:title="TypeOfAdoptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="TypeOfAdoptionMember" xlink:title="definition: AdjustmentsForNewAccountingPronouncementsAxis to TypeOfAdoptionMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="TypeOfAdoptionMember_2" xlink:title="TypeOfAdoptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="TypeOfAdoptionMember_2" xlink:title="definition: AdjustmentsForNewAccountingPronouncementsAxis to TypeOfAdoptionMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NewAccountingPronouncementMember" xlink:label="NewAccountingPronouncementMember" xlink:title="NewAccountingPronouncementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TypeOfAdoptionMember" xlink:to="NewAccountingPronouncementMember" xlink:title="definition: TypeOfAdoptionMember to NewAccountingPronouncementMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="AccountingStandardsUpdate201602Member" xlink:title="AccountingStandardsUpdate201602Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementMember" xlink:to="AccountingStandardsUpdate201602Member" xlink:title="definition: NewAccountingPronouncementMember to AccountingStandardsUpdate201602Member" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201707Member" xlink:label="AccountingStandardsUpdate201707Member" xlink:title="AccountingStandardsUpdate201707Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementMember" xlink:to="AccountingStandardsUpdate201707Member" xlink:title="definition: NewAccountingPronouncementMember to AccountingStandardsUpdate201707Member" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountingStandardsUpdate201802Member" xlink:label="AccountingStandardsUpdate201802Member" xlink:title="AccountingStandardsUpdate201802Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="NewAccountingPronouncementMember" xlink:to="AccountingStandardsUpdate201802Member" xlink:title="definition: NewAccountingPronouncementMember to AccountingStandardsUpdate201802Member" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="RangeAxis" xlink:title="RangeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:to="RangeAxis" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleTable to RangeAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RangeAxis" xlink:to="RangeMember" xlink:title="definition: RangeAxis to RangeMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember_2" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RangeAxis" xlink:to="RangeMember_2" xlink:title="definition: RangeAxis to RangeMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="MinimumMember" xlink:title="MinimumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MinimumMember" xlink:title="definition: RangeMember to MinimumMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="MaximumMember" xlink:title="MaximumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MaximumMember" xlink:title="definition: RangeMember to MaximumMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="StatementEquityComponentsAxis" xlink:title="StatementEquityComponentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:to="StatementEquityComponentsAxis" xlink:title="definition: NewAccountingPronouncementsOrChangeInAccountingPrincipleTable to StatementEquityComponentsAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="EquityComponentDomain" xlink:title="EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementEquityComponentsAxis" xlink:to="EquityComponentDomain" xlink:title="definition: StatementEquityComponentsAxis to EquityComponentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="EquityComponentDomain_2" xlink:title="EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementEquityComponentsAxis" xlink:to="EquityComponentDomain_2" xlink:title="definition: StatementEquityComponentsAxis to EquityComponentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="AccumulatedOtherComprehensiveIncomeMember" xlink:title="AccumulatedOtherComprehensiveIncomeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="AccumulatedOtherComprehensiveIncomeMember" xlink:title="definition: EquityComponentDomain to AccumulatedOtherComprehensiveIncomeMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="RetainedEarningsMember" xlink:title="RetainedEarningsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EquityComponentDomain" xlink:to="RetainedEarningsMember" xlink:title="definition: EquityComponentDomain to RetainedEarningsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="PropertyPlantAndEquipmentLineItems" xlink:title="PropertyPlantAndEquipmentLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentAbstract" xlink:label="PropertyPlantAndEquipmentAbstract" xlink:title="PropertyPlantAndEquipmentAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="PropertyPlantAndEquipmentAbstract" xlink:title="definition: PropertyPlantAndEquipmentLineItems to PropertyPlantAndEquipmentAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AnnualDepreciationRate" xlink:label="AnnualDepreciationRate" xlink:title="AnnualDepreciationRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="AnnualDepreciationRate" xlink:title="definition: PropertyPlantAndEquipmentLineItems to AnnualDepreciationRate" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="PropertyPlantAndEquipmentUsefulLife" xlink:title="PropertyPlantAndEquipmentUsefulLife" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="PropertyPlantAndEquipmentUsefulLife" xlink:title="definition: PropertyPlantAndEquipmentLineItems to PropertyPlantAndEquipmentUsefulLife" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_InitialTermOfLongTermEvergreenContracts" xlink:label="InitialTermOfLongTermEvergreenContracts" xlink:title="InitialTermOfLongTermEvergreenContracts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="InitialTermOfLongTermEvergreenContracts" xlink:title="definition: PropertyPlantAndEquipmentLineItems to InitialTermOfLongTermEvergreenContracts" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="ScheduleOfPropertyPlantAndEquipmentTable" xlink:title="ScheduleOfPropertyPlantAndEquipmentTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="ScheduleOfPropertyPlantAndEquipmentTable" xlink:title="definition: PropertyPlantAndEquipmentLineItems to ScheduleOfPropertyPlantAndEquipmentTable" order="5.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="PropertyPlantAndEquipmentByTypeAxis" xlink:title="PropertyPlantAndEquipmentByTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="PropertyPlantAndEquipmentByTypeAxis" xlink:title="definition: ScheduleOfPropertyPlantAndEquipmentTable to PropertyPlantAndEquipmentByTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="PropertyPlantAndEquipmentTypeDomain" xlink:title="PropertyPlantAndEquipmentTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="PropertyPlantAndEquipmentByTypeAxis" xlink:to="PropertyPlantAndEquipmentTypeDomain" xlink:title="definition: PropertyPlantAndEquipmentByTypeAxis to PropertyPlantAndEquipmentTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="PropertyPlantAndEquipmentTypeDomain_2" xlink:title="PropertyPlantAndEquipmentTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="PropertyPlantAndEquipmentByTypeAxis" xlink:to="PropertyPlantAndEquipmentTypeDomain_2" xlink:title="definition: PropertyPlantAndEquipmentByTypeAxis to PropertyPlantAndEquipmentTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BuildingMember" xlink:label="BuildingMember" xlink:title="BuildingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="BuildingMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to BuildingMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MachineryAndEquipmentMember" xlink:label="MachineryAndEquipmentMember" xlink:title="MachineryAndEquipmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="MachineryAndEquipmentMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to MachineryAndEquipmentMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="FurnitureAndFixturesMember" xlink:title="FurnitureAndFixturesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="FurnitureAndFixturesMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to FurnitureAndFixturesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ComputerEquipmentAndSoftwareRelatedAssetsMember" xlink:label="ComputerEquipmentAndSoftwareRelatedAssetsMember" xlink:title="ComputerEquipmentAndSoftwareRelatedAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="ComputerEquipmentAndSoftwareRelatedAssetsMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to ComputerEquipmentAndSoftwareRelatedAssetsMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ManufacturingFacilityMember" xlink:label="ManufacturingFacilityMember" xlink:title="ManufacturingFacilityMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="ManufacturingFacilityMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to ManufacturingFacilityMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MachineryAndEquipmentForNaturalStoneMiningAndProcessingPlantsAndChemicalPlantsMember" xlink:label="MachineryAndEquipmentForNaturalStoneMiningAndProcessingPlantsAndChemicalPlantsMember" xlink:title="MachineryAndEquipmentForNaturalStoneMiningAndProcessingPlantsAndChemicalPlantsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="MachineryAndEquipmentForNaturalStoneMiningAndProcessingPlantsAndChemicalPlantsMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to MachineryAndEquipmentForNaturalStoneMiningAndProcessingPlantsAndChemicalPlantsMember" order="6.0" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="RangeAxis" xlink:title="definition: ScheduleOfPropertyPlantAndEquipmentTable to RangeAxis" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LeasesDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems" xlink:label="LesseeLeaseDescriptionLineItems" xlink:title="LesseeLeaseDescriptionLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeOperatingLeaseDescriptionAbstract" xlink:label="LesseeOperatingLeaseDescriptionAbstract" xlink:title="LesseeOperatingLeaseDescriptionAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LesseeLeaseDescriptionLineItems" xlink:to="LesseeOperatingLeaseDescriptionAbstract" xlink:title="definition: LesseeLeaseDescriptionLineItems to LesseeOperatingLeaseDescriptionAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_LesseeOperatingLeaseRemainingLeaseTerm" xlink:label="LesseeOperatingLeaseRemainingLeaseTerm" xlink:title="LesseeOperatingLeaseRemainingLeaseTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LesseeLeaseDescriptionLineItems" xlink:to="LesseeOperatingLeaseRemainingLeaseTerm" xlink:title="definition: LesseeLeaseDescriptionLineItems to LesseeOperatingLeaseRemainingLeaseTerm" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="LesseeLeaseDescriptionTable" xlink:title="LesseeLeaseDescriptionTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="LesseeLeaseDescriptionLineItems" xlink:to="LesseeLeaseDescriptionTable" xlink:title="definition: LesseeLeaseDescriptionLineItems to LesseeLeaseDescriptionTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="RangeAxis" xlink:title="RangeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="LesseeLeaseDescriptionTable" xlink:to="RangeAxis" xlink:title="definition: LesseeLeaseDescriptionTable to RangeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RangeAxis" xlink:to="RangeMember" xlink:title="definition: RangeAxis to RangeMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember_2" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RangeAxis" xlink:to="RangeMember_2" xlink:title="definition: RangeAxis to RangeMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="MinimumMember" xlink:title="MinimumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MinimumMember" xlink:title="definition: RangeMember to MinimumMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="MaximumMember" xlink:title="MaximumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MaximumMember" xlink:title="definition: RangeMember to MaximumMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LeasesDetailsCalc01" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RevenueFromContractsWithCustomersDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="DisaggregationOfRevenueLineItems" xlink:title="DisaggregationOfRevenueLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueAbstract" xlink:label="DisaggregationOfRevenueAbstract" xlink:title="DisaggregationOfRevenueAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DisaggregationOfRevenueLineItems" xlink:to="DisaggregationOfRevenueAbstract" xlink:title="definition: DisaggregationOfRevenueLineItems to DisaggregationOfRevenueAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DisaggregationOfRevenueLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: DisaggregationOfRevenueLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="DisaggregationOfRevenueTable" xlink:title="DisaggregationOfRevenueTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DisaggregationOfRevenueLineItems" xlink:to="DisaggregationOfRevenueTable" xlink:title="definition: DisaggregationOfRevenueLineItems to DisaggregationOfRevenueTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="StatementBusinessSegmentsAxis" xlink:title="StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DisaggregationOfRevenueTable" xlink:to="StatementBusinessSegmentsAxis" xlink:title="definition: DisaggregationOfRevenueTable to StatementBusinessSegmentsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain_2" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain_2" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PerformanceMaterialsMember" xlink:label="PerformanceMaterialsMember" xlink:title="PerformanceMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="PerformanceMaterialsMember" xlink:title="definition: SegmentDomain to PerformanceMaterialsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyMineralsMember" xlink:label="SpecialtyMineralsMember" xlink:title="SpecialtyMineralsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="SpecialtyMineralsMember" xlink:title="definition: SegmentDomain to SpecialtyMineralsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoriesMember" xlink:label="RefractoriesMember" xlink:title="RefractoriesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="RefractoriesMember" xlink:title="definition: SegmentDomain to RefractoriesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnergyServicesMember" xlink:label="EnergyServicesMember" xlink:title="EnergyServicesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="EnergyServicesMember" xlink:title="definition: SegmentDomain to EnergyServicesMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="ProductOrServiceAxis" xlink:title="ProductOrServiceAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DisaggregationOfRevenueTable" xlink:to="ProductOrServiceAxis" xlink:title="definition: DisaggregationOfRevenueTable to ProductOrServiceAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain_2" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain_2" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MetalcastingMember" xlink:label="MetalcastingMember" xlink:title="MetalcastingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MetalcastingMember" xlink:title="definition: ProductsAndServicesDomain to MetalcastingMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_HouseholdPersonalCareAndSpecialtyProductsMember" xlink:label="HouseholdPersonalCareAndSpecialtyProductsMember" xlink:title="HouseholdPersonalCareAndSpecialtyProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="HouseholdPersonalCareAndSpecialtyProductsMember" xlink:title="definition: ProductsAndServicesDomain to HouseholdPersonalCareAndSpecialtyProductsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnvironmentalProductsMember" xlink:label="EnvironmentalProductsMember" xlink:title="EnvironmentalProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="EnvironmentalProductsMember" xlink:title="definition: ProductsAndServicesDomain to EnvironmentalProductsMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_BuildingMaterialsMember" xlink:label="BuildingMaterialsMember" xlink:title="BuildingMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="BuildingMaterialsMember" xlink:title="definition: ProductsAndServicesDomain to BuildingMaterialsMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MineralMember" xlink:label="MineralMember" xlink:title="MineralMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MineralMember" xlink:title="definition: ProductsAndServicesDomain to MineralMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PaperPccMember" xlink:label="PaperPccMember" xlink:title="PaperPccMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="PaperPccMember" xlink:title="definition: ProductsAndServicesDomain to PaperPccMember" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyPccMember" xlink:label="SpecialtyPccMember" xlink:title="SpecialtyPccMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="SpecialtyPccMember" xlink:title="definition: ProductsAndServicesDomain to SpecialtyPccMember" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_GroundCalciumCarbonateMember" xlink:label="GroundCalciumCarbonateMember" xlink:title="GroundCalciumCarbonateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="GroundCalciumCarbonateMember" xlink:title="definition: ProductsAndServicesDomain to GroundCalciumCarbonateMember" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TalcMember" xlink:label="TalcMember" xlink:title="TalcMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="TalcMember" xlink:title="definition: ProductsAndServicesDomain to TalcMember" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoryProductsMember" xlink:label="RefractoryProductsMember" xlink:title="RefractoryProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="RefractoryProductsMember" xlink:title="definition: ProductsAndServicesDomain to RefractoryProductsMember" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MetallurgicalProductsMember" xlink:label="MetallurgicalProductsMember" xlink:title="MetallurgicalProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MetallurgicalProductsMember" xlink:title="definition: ProductsAndServicesDomain to MetallurgicalProductsMember" order="11.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BusinessCombinationDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="BusinessAcquisitionLineItems" xlink:title="BusinessAcquisitionLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract" xlink:label="BusinessCombinationConsiderationTransferredAbstract" xlink:title="BusinessCombinationConsiderationTransferredAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationConsiderationTransferredAbstract" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationConsiderationTransferredAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNetAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsOther" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedMineralRights" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedMineralRights" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedMineralRights" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedMineralRights" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedMineralRights" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="Goodwill" xlink:title="Goodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="Goodwill" xlink:title="definition: BusinessAcquisitionLineItems to Goodwill" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesLongTermDebt" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedExpenses" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:label="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:title="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: BusinessAcquisitionLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1" xlink:label="BusinessCombinationConsiderationTransferred1" xlink:title="BusinessCombinationConsiderationTransferred1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationConsiderationTransferred1" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationConsiderationTransferred1" order="20.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill" xlink:label="DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill" xlink:title="DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill" xlink:title="definition: BusinessAcquisitionLineItems to DeferredTaxLiabilitiesGoodwillAndIntangibleAssetsGoodwill" order="21.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:label="AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:title="AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:title="definition: BusinessAcquisitionLineItems to AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" order="22.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="BusinessCombinationAcquisitionRelatedCosts" xlink:title="BusinessCombinationAcquisitionRelatedCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionLineItems" xlink:to="BusinessCombinationAcquisitionRelatedCosts" xlink:title="definition: BusinessAcquisitionLineItems to BusinessCombinationAcquisitionRelatedCosts" order="23.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:title="ScheduleOfBusinessAcquisitionsByAcquisitionTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="BusinessAcquisitionLineItems" xlink:to="ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:title="definition: BusinessAcquisitionLineItems to ScheduleOfBusinessAcquisitionsByAcquisitionTable" order="24.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="BusinessAcquisitionAxis" xlink:title="BusinessAcquisitionAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:to="BusinessAcquisitionAxis" xlink:title="definition: ScheduleOfBusinessAcquisitionsByAcquisitionTable to BusinessAcquisitionAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain_2" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain_2" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SivomaticMember" xlink:label="SivomaticMember" xlink:title="SivomaticMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionAcquireeDomain" xlink:to="SivomaticMember" xlink:title="definition: BusinessAcquisitionAcquireeDomain to SivomaticMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="FiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:to="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="definition: ScheduleOfBusinessAcquisitionsByAcquisitionTable to FiniteLivedIntangibleAssetsByMajorClassAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="TradeNamesMember" xlink:title="TradeNamesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="TradeNamesMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to TradeNamesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="CustomerRelationshipsMember" xlink:title="CustomerRelationshipsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="CustomerRelationshipsMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to CustomerRelationshipsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAxis" xlink:label="RestatementAxis" xlink:title="RestatementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:to="RestatementAxis" xlink:title="definition: ScheduleOfBusinessAcquisitionsByAcquisitionTable to RestatementAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="RestatementDomain" xlink:title="RestatementDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RestatementAxis" xlink:to="RestatementDomain" xlink:title="definition: RestatementAxis to RestatementDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementDomain" xlink:label="RestatementDomain_2" xlink:title="RestatementDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RestatementAxis" xlink:to="RestatementDomain_2" xlink:title="definition: RestatementAxis to RestatementDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioPreviouslyReportedMember" xlink:label="ScenarioPreviouslyReportedMember" xlink:title="ScenarioPreviouslyReportedMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestatementDomain" xlink:to="ScenarioPreviouslyReportedMember" xlink:title="definition: RestatementDomain to ScenarioPreviouslyReportedMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RestatementAdjustmentMember" xlink:label="RestatementAdjustmentMember" xlink:title="RestatementAdjustmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestatementDomain" xlink:to="RestatementAdjustmentMember" xlink:title="definition: RestatementDomain to RestatementAdjustmentMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/RestructuringAndOtherItemsNetDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="RestructuringCostAndReserveLineItems" xlink:title="RestructuringCostAndReserveLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringSettlementAndImpairmentProvisionsAbstract" xlink:label="RestructuringSettlementAndImpairmentProvisionsAbstract" xlink:title="RestructuringSettlementAndImpairmentProvisionsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringSettlementAndImpairmentProvisionsAbstract" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringSettlementAndImpairmentProvisionsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringChargesAbstract" xlink:label="RestructuringChargesAbstract" xlink:title="RestructuringChargesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringChargesAbstract" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringChargesAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringReserveRollForward" xlink:label="RestructuringReserveRollForward" xlink:title="RestructuringReserveRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringReserveRollForward" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringReserveRollForward" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringReserve" xlink:label="RestructuringReserve" xlink:title="RestructuringReserve" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringReserve" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringReserve" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringReserveAccrualAdjustment1" xlink:label="RestructuringReserveAccrualAdjustment1" xlink:title="RestructuringReserveAccrualAdjustment1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringReserveAccrualAdjustment1" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringReserveAccrualAdjustment1" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsForRestructuring" xlink:label="PaymentsForRestructuring" xlink:title="PaymentsForRestructuring" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="PaymentsForRestructuring" xlink:title="definition: RestructuringCostAndReserveLineItems to PaymentsForRestructuring" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringReserveTranslationAndOtherAdjustment" xlink:label="RestructuringReserveTranslationAndOtherAdjustment" xlink:title="RestructuringReserveTranslationAndOtherAdjustment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringReserveTranslationAndOtherAdjustment" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringReserveTranslationAndOtherAdjustment" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetImpairmentCharges" xlink:label="AssetImpairmentCharges" xlink:title="AssetImpairmentCharges" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="AssetImpairmentCharges" xlink:title="definition: RestructuringCostAndReserveLineItems to AssetImpairmentCharges" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeveranceCosts1" xlink:label="SeveranceCosts1" xlink:title="SeveranceCosts1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="SeveranceCosts1" xlink:title="definition: RestructuringCostAndReserveLineItems to SeveranceCosts1" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherRestructuringCosts" xlink:label="OtherRestructuringCosts" xlink:title="OtherRestructuringCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="OtherRestructuringCosts" xlink:title="definition: RestructuringCostAndReserveLineItems to OtherRestructuringCosts" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="RestructuringCharges" xlink:title="RestructuringCharges" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="RestructuringCharges" xlink:title="definition: RestructuringCostAndReserveLineItems to RestructuringCharges" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EffectOnFutureEarningsAmount" xlink:label="EffectOnFutureEarningsAmount" xlink:title="EffectOnFutureEarningsAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="EffectOnFutureEarningsAmount" xlink:title="definition: RestructuringCostAndReserveLineItems to EffectOnFutureEarningsAmount" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainLossOnDispositionOfAssets" xlink:label="GainLossOnDispositionOfAssets" xlink:title="GainLossOnDispositionOfAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="GainLossOnDispositionOfAssets" xlink:title="definition: RestructuringCostAndReserveLineItems to GainLossOnDispositionOfAssets" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="ScheduleOfRestructuringAndRelatedCostsTable" xlink:title="ScheduleOfRestructuringAndRelatedCostsTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="RestructuringCostAndReserveLineItems" xlink:to="ScheduleOfRestructuringAndRelatedCostsTable" xlink:title="definition: RestructuringCostAndReserveLineItems to ScheduleOfRestructuringAndRelatedCostsTable" order="14.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="StatementBusinessSegmentsAxis" xlink:title="StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfRestructuringAndRelatedCostsTable" xlink:to="StatementBusinessSegmentsAxis" xlink:title="definition: ScheduleOfRestructuringAndRelatedCostsTable to StatementBusinessSegmentsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain_2" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain_2" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PerformanceMaterialsMember" xlink:label="PerformanceMaterialsMember" xlink:title="PerformanceMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="PerformanceMaterialsMember" xlink:title="definition: SegmentDomain to PerformanceMaterialsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyMineralsMember" xlink:label="SpecialtyMineralsMember" xlink:title="SpecialtyMineralsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="SpecialtyMineralsMember" xlink:title="definition: SegmentDomain to SpecialtyMineralsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoriesMember" xlink:label="RefractoriesMember" xlink:title="RefractoriesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="RefractoriesMember" xlink:title="definition: SegmentDomain to RefractoriesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnergyServicesMember" xlink:label="EnergyServicesMember" xlink:title="EnergyServicesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="EnergyServicesMember" xlink:title="definition: SegmentDomain to EnergyServicesMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateMember" xlink:label="CorporateMember" xlink:title="CorporateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="CorporateMember" xlink:title="definition: SegmentDomain to CorporateMember" order="5.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockbasedCompensationStockAwardAndIncentivePlanAndStockOptionsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:label="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:title="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsAndMethodologyAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValueAbstract" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AggregateIntrinsicValueAbstract" xlink:label="AggregateIntrinsicValueAbstract" xlink:title="AggregateIntrinsicValueAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="AggregateIntrinsicValueAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to AggregateIntrinsicValueAbstract" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharePrice" xlink:label="SharePrice" xlink:title="SharePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharePrice" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageIntrinsicValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageIntrinsicValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageIntrinsicValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageIntrinsicValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisedInPeriodWeightedAverageIntrinsicValue" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:title="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:title="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsOtherShareIncreaseDecreaseInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsOtherShareIncreaseDecreaseInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsOtherShareIncreaseDecreaseInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsOtherShareIncreaseDecreaseInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsOtherShareIncreaseDecreaseInPeriodWeightedAverageExercisePrice" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" order="20.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" order="21.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" order="22.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" order="23.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" order="24.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod" order="25.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:title="StockIssuedDuringPeriodSharesStockOptionsExercised" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to StockIssuedDuringPeriodSharesStockOptionsExercised" order="26.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" order="27.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" order="28.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" order="29.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" order="30.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" order="31.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" order="32.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" order="33.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" order="34.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" order="35.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" order="36.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="ShareBasedCompensation" xlink:title="ShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensation" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensation" order="37.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:label="EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:title="EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense" order="38.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionForfeitureRateAssumed" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionForfeitureRateAssumed" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionForfeitureRateAssumed" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionForfeitureRateAssumed" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionForfeitureRateAssumed" order="39.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="40.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" order="41.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" order="42.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" order="43.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="AwardTypeAxis" xlink:title="AwardTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="AwardTypeAxis" xlink:title="definition: ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable to AwardTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="EmployeeStockOptionMember" xlink:title="EmployeeStockOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="EmployeeStockOptionMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to EmployeeStockOptionMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NonvestedStockOptionsMember" xlink:label="NonvestedStockOptionsMember" xlink:title="NonvestedStockOptionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="NonvestedStockOptionsMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to NonvestedStockOptionsMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockbasedCompensationRestrictedStockDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:label="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:title="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:title="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:title="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="ShareBasedCompensation" xlink:title="ShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensation" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensation" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ReversalsOfCompensationExpense" xlink:label="ReversalsOfCompensationExpense" xlink:title="ReversalsOfCompensationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ReversalsOfCompensationExpense" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ReversalsOfCompensationExpense" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" order="16.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="AwardTypeAxis" xlink:title="AwardTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="AwardTypeAxis" xlink:title="definition: ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable to AwardTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NonvestedStockOptionsMember" xlink:label="NonvestedStockOptionsMember" xlink:title="NonvestedStockOptionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="NonvestedStockOptionsMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to NonvestedStockOptionsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="RestrictedStockMember" xlink:title="RestrictedStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="RestrictedStockMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to RestrictedStockMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/EarningsPerShareEpsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:title="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AntidilutiveSecuritiesExcludedFromEarningsPerShareCalculationAbstract" xlink:label="AntidilutiveSecuritiesExcludedFromEarningsPerShareCalculationAbstract" xlink:title="AntidilutiveSecuritiesExcludedFromEarningsPerShareCalculationAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="AntidilutiveSecuritiesExcludedFromEarningsPerShareCalculationAbstract" xlink:title="definition: AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems to AntidilutiveSecuritiesExcludedFromEarningsPerShareCalculationAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:title="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:title="definition: AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems to AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:title="ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:title="definition: AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems to ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:title="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:title="definition: ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable to AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="AntidilutiveSecuritiesNameDomain" xlink:title="AntidilutiveSecuritiesNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="AntidilutiveSecuritiesNameDomain" xlink:title="definition: AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis to AntidilutiveSecuritiesNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="AntidilutiveSecuritiesNameDomain_2" xlink:title="AntidilutiveSecuritiesNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="AntidilutiveSecuritiesNameDomain_2" xlink:title="definition: AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis to AntidilutiveSecuritiesNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="EmployeeStockOptionMember" xlink:title="EmployeeStockOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AntidilutiveSecuritiesNameDomain" xlink:to="EmployeeStockOptionMember" xlink:title="definition: AntidilutiveSecuritiesNameDomain to EmployeeStockOptionMember" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/IncomeTaxesDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems" xlink:label="OperatingLossCarryforwardsLineItems" xlink:title="OperatingLossCarryforwardsLineItems" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_OperatingLossCarryforwardsAbstract" xlink:label="OperatingLossCarryforwardsAbstract" xlink:title="OperatingLossCarryforwardsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="OperatingLossCarryforwardsLineItems" xlink:to="OperatingLossCarryforwardsAbstract" xlink:title="definition: OperatingLossCarryforwardsLineItems to OperatingLossCarryforwardsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:label="OperatingLossCarryforwards" xlink:title="OperatingLossCarryforwards" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="OperatingLossCarryforwardsLineItems" xlink:to="OperatingLossCarryforwards" xlink:title="definition: OperatingLossCarryforwardsLineItems to OperatingLossCarryforwards" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_OperatingLossCarryforwardsExpirationYear" xlink:label="OperatingLossCarryforwardsExpirationYear" xlink:title="OperatingLossCarryforwardsExpirationYear" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="OperatingLossCarryforwardsLineItems" xlink:to="OperatingLossCarryforwardsExpirationYear" xlink:title="definition: OperatingLossCarryforwardsLineItems to OperatingLossCarryforwardsExpirationYear" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable" xlink:label="OperatingLossCarryforwardsTable" xlink:title="OperatingLossCarryforwardsTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="OperatingLossCarryforwardsLineItems" xlink:to="OperatingLossCarryforwardsTable" xlink:title="definition: OperatingLossCarryforwardsLineItems to OperatingLossCarryforwardsTable" order="4.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TaxCreditCarryforwardAxis" xlink:label="TaxCreditCarryforwardAxis" xlink:title="TaxCreditCarryforwardAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="OperatingLossCarryforwardsTable" xlink:to="TaxCreditCarryforwardAxis" xlink:title="definition: OperatingLossCarryforwardsTable to TaxCreditCarryforwardAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:label="TaxCreditCarryforwardNameDomain" xlink:title="TaxCreditCarryforwardNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="TaxCreditCarryforwardAxis" xlink:to="TaxCreditCarryforwardNameDomain" xlink:title="definition: TaxCreditCarryforwardAxis to TaxCreditCarryforwardNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:label="TaxCreditCarryforwardNameDomain_2" xlink:title="TaxCreditCarryforwardNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="TaxCreditCarryforwardAxis" xlink:to="TaxCreditCarryforwardNameDomain_2" xlink:title="definition: TaxCreditCarryforwardAxis to TaxCreditCarryforwardNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FiniteLivedTaxLossCarryForwardsMember" xlink:label="FiniteLivedTaxLossCarryForwardsMember" xlink:title="FiniteLivedTaxLossCarryForwardsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TaxCreditCarryforwardNameDomain" xlink:to="FiniteLivedTaxLossCarryForwardsMember" xlink:title="definition: TaxCreditCarryforwardNameDomain to FiniteLivedTaxLossCarryForwardsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_IndefiniteLivedTaxLossCarryForwardsMember" xlink:label="IndefiniteLivedTaxLossCarryForwardsMember" xlink:title="IndefiniteLivedTaxLossCarryForwardsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TaxCreditCarryforwardNameDomain" xlink:to="IndefiniteLivedTaxLossCarryForwardsMember" xlink:title="definition: TaxCreditCarryforwardNameDomain to IndefiniteLivedTaxLossCarryForwardsMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/IncomeTaxesDetailsCalc01" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/InventoriesDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/PropertyPlantAndEquipmentDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="PropertyPlantAndEquipmentLineItems" xlink:title="PropertyPlantAndEquipmentLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNetAbstract" xlink:label="PropertyPlantAndEquipmentNetAbstract" xlink:title="PropertyPlantAndEquipmentNetAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="PropertyPlantAndEquipmentNetAbstract" xlink:title="definition: PropertyPlantAndEquipmentLineItems to PropertyPlantAndEquipmentNetAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="PropertyPlantAndEquipmentGross" xlink:title="PropertyPlantAndEquipmentGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="PropertyPlantAndEquipmentGross" xlink:title="definition: PropertyPlantAndEquipmentLineItems to PropertyPlantAndEquipmentGross" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:title="AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:title="definition: PropertyPlantAndEquipmentLineItems to AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="PropertyPlantAndEquipmentNet" xlink:title="PropertyPlantAndEquipmentNet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="PropertyPlantAndEquipmentNet" xlink:title="definition: PropertyPlantAndEquipmentLineItems to PropertyPlantAndEquipmentNet" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DepreciationAndDepletionExpense" xlink:label="DepreciationAndDepletionExpense" xlink:title="DepreciationAndDepletionExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="DepreciationAndDepletionExpense" xlink:title="definition: PropertyPlantAndEquipmentLineItems to DepreciationAndDepletionExpense" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="ScheduleOfPropertyPlantAndEquipmentTable" xlink:title="ScheduleOfPropertyPlantAndEquipmentTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="PropertyPlantAndEquipmentLineItems" xlink:to="ScheduleOfPropertyPlantAndEquipmentTable" xlink:title="definition: PropertyPlantAndEquipmentLineItems to ScheduleOfPropertyPlantAndEquipmentTable" order="6.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="PropertyPlantAndEquipmentByTypeAxis" xlink:title="PropertyPlantAndEquipmentByTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="PropertyPlantAndEquipmentByTypeAxis" xlink:title="definition: ScheduleOfPropertyPlantAndEquipmentTable to PropertyPlantAndEquipmentByTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="PropertyPlantAndEquipmentTypeDomain" xlink:title="PropertyPlantAndEquipmentTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="PropertyPlantAndEquipmentByTypeAxis" xlink:to="PropertyPlantAndEquipmentTypeDomain" xlink:title="definition: PropertyPlantAndEquipmentByTypeAxis to PropertyPlantAndEquipmentTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="PropertyPlantAndEquipmentTypeDomain_2" xlink:title="PropertyPlantAndEquipmentTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="PropertyPlantAndEquipmentByTypeAxis" xlink:to="PropertyPlantAndEquipmentTypeDomain_2" xlink:title="definition: PropertyPlantAndEquipmentByTypeAxis to PropertyPlantAndEquipmentTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MineralRightsAndReservesMember" xlink:label="MineralRightsAndReservesMember" xlink:title="MineralRightsAndReservesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="MineralRightsAndReservesMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to MineralRightsAndReservesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LandMember" xlink:label="LandMember" xlink:title="LandMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="LandMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to LandMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BuildingMember" xlink:label="BuildingMember" xlink:title="BuildingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="BuildingMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to BuildingMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MachineryAndEquipmentMember" xlink:label="MachineryAndEquipmentMember" xlink:title="MachineryAndEquipmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="MachineryAndEquipmentMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to MachineryAndEquipmentMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FurnitureAndFixturesAndOtherMember" xlink:label="FurnitureAndFixturesAndOtherMember" xlink:title="FurnitureAndFixturesAndOtherMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="FurnitureAndFixturesAndOtherMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to FurnitureAndFixturesAndOtherMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="ConstructionInProgressMember" xlink:title="ConstructionInProgressMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PropertyPlantAndEquipmentTypeDomain" xlink:to="ConstructionInProgressMember" xlink:title="definition: PropertyPlantAndEquipmentTypeDomain to ConstructionInProgressMember" order="6.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:label="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:title="AcquiredFiniteLivedIntangibleAssetsLineItems" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FiniteLivedIntangibleAssetsAbstract" xlink:label="FiniteLivedIntangibleAssetsAbstract" xlink:title="FiniteLivedIntangibleAssetsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAbstract" xlink:title="definition: AcquiredFiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="FiniteLivedIntangibleAssetUsefulLife" xlink:title="FiniteLivedIntangibleAssetUsefulLife" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetUsefulLife" xlink:title="definition: AcquiredFiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetUsefulLife" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="FiniteLivedIntangibleAssetsGross" xlink:title="FiniteLivedIntangibleAssetsGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsGross" xlink:title="definition: AcquiredFiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsGross" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:title="FiniteLivedIntangibleAssetsAccumulatedAmortization" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:title="definition: AcquiredFiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAccumulatedAmortization" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" xlink:label="ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" xlink:title="ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="AcquiredFiniteLivedIntangibleAssetsLineItems" xlink:to="ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" xlink:title="definition: AcquiredFiniteLivedIntangibleAssetsLineItems to ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" order="5.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="FiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable" xlink:to="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="definition: ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable to FiniteLivedIntangibleAssetsByMajorClassAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="TradeNamesMember" xlink:title="TradeNamesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="TradeNamesMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to TradeNamesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember" xlink:label="TechnologyBasedIntangibleAssetsMember" xlink:title="TechnologyBasedIntangibleAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="TechnologyBasedIntangibleAssetsMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to TechnologyBasedIntangibleAssetsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PatentsAndTrademarksMember" xlink:label="PatentsAndTrademarksMember" xlink:title="PatentsAndTrademarksMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="PatentsAndTrademarksMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to PatentsAndTrademarksMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="CustomerRelationshipsMember" xlink:title="CustomerRelationshipsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="CustomerRelationshipsMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to CustomerRelationshipsMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="GoodwillLineItems" xlink:title="GoodwillLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillRollForward" xlink:label="GoodwillRollForward" xlink:title="GoodwillRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="GoodwillRollForward" xlink:title="definition: GoodwillLineItems to GoodwillRollForward" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="Goodwill" xlink:title="Goodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="Goodwill" xlink:title="definition: GoodwillLineItems to Goodwill" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ChangeInGoodwillRelatingToAbstract" xlink:label="ChangeInGoodwillRelatingToAbstract" xlink:title="ChangeInGoodwillRelatingToAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="ChangeInGoodwillRelatingToAbstract" xlink:title="definition: GoodwillLineItems to ChangeInGoodwillRelatingToAbstract" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod" xlink:label="GoodwillAcquiredDuringPeriod" xlink:title="GoodwillAcquiredDuringPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="GoodwillAcquiredDuringPeriod" xlink:title="definition: GoodwillLineItems to GoodwillAcquiredDuringPeriod" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss" xlink:label="GoodwillForeignCurrencyTranslationGainLoss" xlink:title="GoodwillForeignCurrencyTranslationGainLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="GoodwillForeignCurrencyTranslationGainLoss" xlink:title="definition: GoodwillLineItems to GoodwillForeignCurrencyTranslationGainLoss" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillPeriodIncreaseDecrease" xlink:label="GoodwillPeriodIncreaseDecrease" xlink:title="GoodwillPeriodIncreaseDecrease" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="GoodwillLineItems" xlink:to="GoodwillPeriodIncreaseDecrease" xlink:title="definition: GoodwillLineItems to GoodwillPeriodIncreaseDecrease" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="ScheduleOfGoodwillTable" xlink:title="ScheduleOfGoodwillTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="GoodwillLineItems" xlink:to="ScheduleOfGoodwillTable" xlink:title="definition: GoodwillLineItems to ScheduleOfGoodwillTable" order="7.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="StatementBusinessSegmentsAxis" xlink:title="StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfGoodwillTable" xlink:to="StatementBusinessSegmentsAxis" xlink:title="definition: ScheduleOfGoodwillTable to StatementBusinessSegmentsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain_2" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain_2" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PerformanceMaterialsMember" xlink:label="PerformanceMaterialsMember" xlink:title="PerformanceMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="PerformanceMaterialsMember" xlink:title="definition: SegmentDomain to PerformanceMaterialsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyMineralsMember" xlink:label="SpecialtyMineralsMember" xlink:title="SpecialtyMineralsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="SpecialtyMineralsMember" xlink:title="definition: SegmentDomain to SpecialtyMineralsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoriesMember" xlink:label="RefractoriesMember" xlink:title="RefractoriesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="RefractoriesMember" xlink:title="definition: SegmentDomain to RefractoriesMember" order="3.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/GoodwillAndOtherIntangibleAssetsAcquiredIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="FiniteLivedIntangibleAssetsLineItems" xlink:title="FiniteLivedIntangibleAssetsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract" xlink:label="FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract" xlink:title="FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsFutureAmortizationExpenseAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="AmortizationOfIntangibleAssets" xlink:title="AmortizationOfIntangibleAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="AmortizationOfIntangibleAssets" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to AmortizationOfIntangibleAssets" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseYearThree" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseYearFour" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseYearFive" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" xlink:label="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" xlink:title="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:title="ScheduleOfFiniteLivedIntangibleAssetsTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="FiniteLivedIntangibleAssetsLineItems" xlink:to="ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:title="definition: FiniteLivedIntangibleAssetsLineItems to ScheduleOfFiniteLivedIntangibleAssetsTable" order="9.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="FiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:to="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:title="definition: ScheduleOfFiniteLivedIntangibleAssetsTable to FiniteLivedIntangibleAssetsByMajorClassAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="FiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="FiniteLivedIntangibleAssetsMajorClassNameDomain_2" xlink:title="definition: FiniteLivedIntangibleAssetsByMajorClassAxis to FiniteLivedIntangibleAssetsMajorClassNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AcquiredFiniteLivedIntangibleAssetsMember" xlink:label="AcquiredFiniteLivedIntangibleAssetsMember" xlink:title="AcquiredFiniteLivedIntangibleAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="AcquiredFiniteLivedIntangibleAssetsMember" xlink:title="definition: FiniteLivedIntangibleAssetsMajorClassNameDomain to AcquiredFiniteLivedIntangibleAssetsMember" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/DerivativeFinancialInstrumentsAndHedgingActivitiesDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativesFairValueLineItems" xlink:label="DerivativesFairValueLineItems" xlink:title="DerivativesFairValueLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFairValueOfDerivativeNetAbstract" xlink:label="DerivativeFairValueOfDerivativeNetAbstract" xlink:title="DerivativeFairValueOfDerivativeNetAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="DerivativeFairValueOfDerivativeNetAbstract" xlink:title="definition: DerivativesFairValueLineItems to DerivativeFairValueOfDerivativeNetAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="DerivativeNotionalAmount" xlink:title="DerivativeNotionalAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="DerivativeNotionalAmount" xlink:title="definition: DerivativesFairValueLineItems to DerivativeNotionalAmount" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgeAssetsAtFairValue" xlink:label="FairValueHedgeAssetsAtFairValue" xlink:title="FairValueHedgeAssetsAtFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="FairValueHedgeAssetsAtFairValue" xlink:title="definition: DerivativesFairValueLineItems to FairValueHedgeAssetsAtFairValue" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueHedgeLiabilitiesAtFairValue" xlink:label="FairValueHedgeLiabilitiesAtFairValue" xlink:title="FairValueHedgeLiabilitiesAtFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="FairValueHedgeLiabilitiesAtFairValue" xlink:title="definition: DerivativesFairValueLineItems to FairValueHedgeLiabilitiesAtFairValue" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld" xlink:label="DerivativeNumberOfInstrumentsHeld" xlink:title="DerivativeNumberOfInstrumentsHeld" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="DerivativeNumberOfInstrumentsHeld" xlink:title="definition: DerivativesFairValueLineItems to DerivativeNumberOfInstrumentsHeld" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="OtherNonoperatingIncomeExpense" xlink:title="OtherNonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativesFairValueLineItems" xlink:to="OtherNonoperatingIncomeExpense" xlink:title="definition: DerivativesFairValueLineItems to OtherNonoperatingIncomeExpense" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:label="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:title="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DerivativesFairValueLineItems" xlink:to="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:title="definition: DerivativesFairValueLineItems to FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" order="7.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:title="DerivativeInstrumentsGainLossByHedgingRelationshipAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:to="DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:title="definition: FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable to DerivativeInstrumentsGainLossByHedgingRelationshipAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="HedgingRelationshipDomain" xlink:title="HedgingRelationshipDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:to="HedgingRelationshipDomain" xlink:title="definition: DerivativeInstrumentsGainLossByHedgingRelationshipAxis to HedgingRelationshipDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="HedgingRelationshipDomain_2" xlink:title="HedgingRelationshipDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:to="HedgingRelationshipDomain_2" xlink:title="definition: DerivativeInstrumentsGainLossByHedgingRelationshipAxis to HedgingRelationshipDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashFlowHedgingMember" xlink:label="CashFlowHedgingMember" xlink:title="CashFlowHedgingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="HedgingRelationshipDomain" xlink:to="CashFlowHedgingMember" xlink:title="definition: HedgingRelationshipDomain to CashFlowHedgingMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="HedgingDesignationAxis" xlink:title="HedgingDesignationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:to="HedgingDesignationAxis" xlink:title="definition: FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable to HedgingDesignationAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="HedgingDesignationDomain" xlink:title="HedgingDesignationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="HedgingDesignationAxis" xlink:to="HedgingDesignationDomain" xlink:title="definition: HedgingDesignationAxis to HedgingDesignationDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="HedgingDesignationDomain_2" xlink:title="HedgingDesignationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="HedgingDesignationAxis" xlink:to="HedgingDesignationDomain_2" xlink:title="definition: HedgingDesignationAxis to HedgingDesignationDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="DesignatedAsHedgingInstrumentMember" xlink:title="DesignatedAsHedgingInstrumentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="HedgingDesignationDomain" xlink:to="DesignatedAsHedgingInstrumentMember" xlink:title="definition: HedgingDesignationDomain to DesignatedAsHedgingInstrumentMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="DerivativeInstrumentRiskAxis" xlink:title="DerivativeInstrumentRiskAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:to="DerivativeInstrumentRiskAxis" xlink:title="definition: FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable to DerivativeInstrumentRiskAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="DerivativeContractTypeDomain" xlink:title="DerivativeContractTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DerivativeInstrumentRiskAxis" xlink:to="DerivativeContractTypeDomain" xlink:title="definition: DerivativeInstrumentRiskAxis to DerivativeContractTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="DerivativeContractTypeDomain_2" xlink:title="DerivativeContractTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DerivativeInstrumentRiskAxis" xlink:to="DerivativeContractTypeDomain_2" xlink:title="definition: DerivativeInstrumentRiskAxis to DerivativeContractTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="ForeignExchangeForwardMember" xlink:title="ForeignExchangeForwardMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativeContractTypeDomain" xlink:to="ForeignExchangeForwardMember" xlink:title="definition: DerivativeContractTypeDomain to ForeignExchangeForwardMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRateSwapMember" xlink:label="InterestRateSwapMember" xlink:title="InterestRateSwapMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativeContractTypeDomain" xlink:to="InterestRateSwapMember" xlink:title="definition: DerivativeContractTypeDomain to InterestRateSwapMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CrossCurrencyInterestRateContractMember" xlink:label="CrossCurrencyInterestRateContractMember" xlink:title="CrossCurrencyInterestRateContractMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DerivativeContractTypeDomain" xlink:to="CrossCurrencyInterestRateContractMember" xlink:title="definition: DerivativeContractTypeDomain to CrossCurrencyInterestRateContractMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="BalanceSheetLocationAxis" xlink:title="BalanceSheetLocationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:to="BalanceSheetLocationAxis" xlink:title="definition: FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable to BalanceSheetLocationAxis" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="BalanceSheetLocationDomain" xlink:title="BalanceSheetLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="BalanceSheetLocationAxis" xlink:to="BalanceSheetLocationDomain" xlink:title="definition: BalanceSheetLocationAxis to BalanceSheetLocationDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="BalanceSheetLocationDomain_2" xlink:title="BalanceSheetLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="BalanceSheetLocationAxis" xlink:to="BalanceSheetLocationDomain_2" xlink:title="definition: BalanceSheetLocationAxis to BalanceSheetLocationDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember" xlink:label="OtherNoncurrentLiabilitiesMember" xlink:title="OtherNoncurrentLiabilitiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BalanceSheetLocationDomain" xlink:to="OtherNoncurrentLiabilitiesMember" xlink:title="definition: BalanceSheetLocationDomain to OtherNoncurrentLiabilitiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_OtherAssetsAndDeferredChargesMember" xlink:label="OtherAssetsAndDeferredChargesMember" xlink:title="OtherAssetsAndDeferredChargesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BalanceSheetLocationDomain" xlink:to="OtherAssetsAndDeferredChargesMember" xlink:title="definition: BalanceSheetLocationDomain to OtherAssetsAndDeferredChargesMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/FairValueOfFinancialInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:title="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalFairValueElementsAbstract" xlink:label="AdditionalFairValueElementsAbstract" xlink:title="AdditionalFairValueElementsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="AdditionalFairValueElementsAbstract" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to AdditionalFairValueElementsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DeferredCompensationPlanAssetFairValueDisclosure" xlink:label="DeferredCompensationPlanAssetFairValueDisclosure" xlink:title="DeferredCompensationPlanAssetFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="DeferredCompensationPlanAssetFairValueDisclosure" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to DeferredCompensationPlanAssetFairValueDisclosure" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SupplementaryPensionPlanAssetFairValueDisclosure" xlink:label="SupplementaryPensionPlanAssetFairValueDisclosure" xlink:title="SupplementaryPensionPlanAssetFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="SupplementaryPensionPlanAssetFairValueDisclosure" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to SupplementaryPensionPlanAssetFairValueDisclosure" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure" xlink:label="ForeignCurrencyContractAssetFairValueDisclosure" xlink:title="ForeignCurrencyContractAssetFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="ForeignCurrencyContractAssetFairValueDisclosure" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to ForeignCurrencyContractAssetFairValueDisclosure" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_InterestRateSwapAssetsFairValueDisclosure" xlink:label="InterestRateSwapAssetsFairValueDisclosure" xlink:title="InterestRateSwapAssetsFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="InterestRateSwapAssetsFairValueDisclosure" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to InterestRateSwapAssetsFairValueDisclosure" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure" xlink:label="CashAndCashEquivalentsFairValueDisclosure" xlink:title="CashAndCashEquivalentsFairValueDisclosure" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="CashAndCashEquivalentsFairValueDisclosure" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to CashAndCashEquivalentsFairValueDisclosure" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet" xlink:label="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet" xlink:title="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:title="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems to FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" order="8.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="FairValueByMeasurementFrequencyAxis" xlink:title="FairValueByMeasurementFrequencyAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="FairValueByMeasurementFrequencyAxis" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable to FairValueByMeasurementFrequencyAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="FairValueMeasurementFrequencyDomain" xlink:title="FairValueMeasurementFrequencyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FairValueByMeasurementFrequencyAxis" xlink:to="FairValueMeasurementFrequencyDomain" xlink:title="definition: FairValueByMeasurementFrequencyAxis to FairValueMeasurementFrequencyDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="FairValueMeasurementFrequencyDomain_2" xlink:title="FairValueMeasurementFrequencyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FairValueByMeasurementFrequencyAxis" xlink:to="FairValueMeasurementFrequencyDomain_2" xlink:title="definition: FairValueByMeasurementFrequencyAxis to FairValueMeasurementFrequencyDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="FairValueMeasurementsRecurringMember" xlink:title="FairValueMeasurementsRecurringMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementFrequencyDomain" xlink:to="FairValueMeasurementsRecurringMember" xlink:title="definition: FairValueMeasurementFrequencyDomain to FairValueMeasurementsRecurringMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="FairValueByFairValueHierarchyLevelAxis" xlink:title="FairValueByFairValueHierarchyLevelAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="FairValueByFairValueHierarchyLevelAxis" xlink:title="definition: FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable to FairValueByFairValueHierarchyLevelAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="FairValueInputsLevel1Member" xlink:title="FairValueInputsLevel1Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel1Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel1Member" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="FairValueInputsLevel2Member" xlink:title="FairValueInputsLevel2Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel2Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel2Member" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="FairValueInputsLevel3Member" xlink:title="FairValueInputsLevel3Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel3Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel3Member" order="3.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/FinancialInstrumentsAndConcentrationsOfCreditRiskDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LongtermDebtAndCommitmentsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="DebtInstrumentLineItems" xlink:title="DebtInstrumentLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentsAbstract" xlink:label="DebtInstrumentsAbstract" xlink:title="DebtInstrumentsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentsAbstract" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShortTermBorrowingsAbstract" xlink:label="ShortTermBorrowingsAbstract" xlink:title="ShortTermBorrowingsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="ShortTermBorrowingsAbstract" xlink:title="definition: DebtInstrumentLineItems to ShortTermBorrowingsAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaturitiesOfLongTermDebtAbstract" xlink:label="MaturitiesOfLongTermDebtAbstract" xlink:title="MaturitiesOfLongTermDebtAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="MaturitiesOfLongTermDebtAbstract" xlink:title="definition: DebtInstrumentLineItems to MaturitiesOfLongTermDebtAbstract" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpenseAbstract" xlink:label="InterestExpenseAbstract" xlink:title="InterestExpenseAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="InterestExpenseAbstract" xlink:title="definition: DebtInstrumentLineItems to InterestExpenseAbstract" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestCostsIncurred" xlink:label="InterestCostsIncurred" xlink:title="InterestCostsIncurred" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="InterestCostsIncurred" xlink:title="definition: DebtInstrumentLineItems to InterestCostsIncurred" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestCostsIncurredCapitalized" xlink:label="InterestCostsIncurredCapitalized" xlink:title="InterestCostsIncurredCapitalized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="InterestCostsIncurredCapitalized" xlink:title="definition: DebtInstrumentLineItems to InterestCostsIncurredCapitalized" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" xlink:label="LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" xlink:title="LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShortTermBorrowings" xlink:label="ShortTermBorrowings" xlink:title="ShortTermBorrowings" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="ShortTermBorrowings" xlink:title="definition: DebtInstrumentLineItems to ShortTermBorrowings" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShortTermDebtWeightedAverageInterestRate" xlink:label="ShortTermDebtWeightedAverageInterestRate" xlink:title="ShortTermDebtWeightedAverageInterestRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="ShortTermDebtWeightedAverageInterestRate" xlink:title="definition: DebtInstrumentLineItems to ShortTermDebtWeightedAverageInterestRate" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:label="DebtLongtermAndShorttermCombinedAmount" xlink:title="DebtLongtermAndShorttermCombinedAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtLongtermAndShorttermCombinedAmount" xlink:title="definition: DebtInstrumentLineItems to DebtLongtermAndShorttermCombinedAmount" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="LongTermDebtCurrent" xlink:title="LongTermDebtCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtCurrent" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtCurrent" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtNoncurrent" xlink:label="LongTermDebtNoncurrent" xlink:title="LongTermDebtNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LongTermDebtNoncurrent" xlink:title="definition: DebtInstrumentLineItems to LongTermDebtNoncurrent" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="DebtInstrumentUnamortizedDiscount" xlink:title="DebtInstrumentUnamortizedDiscount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentUnamortizedDiscount" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentUnamortizedDiscount" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="DebtInstrumentMaturityDate" xlink:title="DebtInstrumentMaturityDate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentMaturityDate" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentMaturityDate" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="LineOfCreditFacilityMaximumBorrowingCapacity" xlink:title="LineOfCreditFacilityMaximumBorrowingCapacity" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LineOfCreditFacilityMaximumBorrowingCapacity" xlink:title="definition: DebtInstrumentLineItems to LineOfCreditFacilityMaximumBorrowingCapacity" order="20.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding" xlink:label="LineOfCreditFacilityFairValueOfAmountOutstanding" xlink:title="LineOfCreditFacilityFairValueOfAmountOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LineOfCreditFacilityFairValueOfAmountOutstanding" xlink:title="definition: DebtInstrumentLineItems to LineOfCreditFacilityFairValueOfAmountOutstanding" order="21.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="DebtInstrumentInterestRateStatedPercentage" xlink:title="DebtInstrumentInterestRateStatedPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentInterestRateStatedPercentage" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentInterestRateStatedPercentage" order="22.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="DebtInstrumentBasisSpreadOnVariableRate1" xlink:title="DebtInstrumentBasisSpreadOnVariableRate1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentBasisSpreadOnVariableRate1" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentBasisSpreadOnVariableRate1" order="23.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate" xlink:label="DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate" xlink:title="DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentIncreaseDecreaseInBasisSpreadOnVariableRate" order="24.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DebtInstrumentIssuePricePercentage" xlink:label="DebtInstrumentIssuePricePercentage" xlink:title="DebtInstrumentIssuePricePercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentIssuePricePercentage" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentIssuePricePercentage" order="25.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AmortizationRateOnNotes" xlink:label="AmortizationRateOnNotes" xlink:title="AmortizationRateOnNotes" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="AmortizationRateOnNotes" xlink:title="definition: DebtInstrumentLineItems to AmortizationRateOnNotes" order="26.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="DebtInstrumentCarryingAmount" xlink:title="DebtInstrumentCarryingAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentCarryingAmount" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentCarryingAmount" order="27.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="LettersOfCreditOutstandingAmount" xlink:title="LettersOfCreditOutstandingAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LettersOfCreditOutstandingAmount" xlink:title="definition: DebtInstrumentLineItems to LettersOfCreditOutstandingAmount" order="28.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RequiredAnnualAmortization" xlink:label="RequiredAnnualAmortization" xlink:title="RequiredAnnualAmortization" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="RequiredAnnualAmortization" xlink:title="definition: DebtInstrumentLineItems to RequiredAnnualAmortization" order="29.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt" xlink:label="RepaymentsOfLongTermDebt" xlink:title="RepaymentsOfLongTermDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="RepaymentsOfLongTermDebt" xlink:title="definition: DebtInstrumentLineItems to RepaymentsOfLongTermDebt" order="30.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DebtInstrumentNetLeverageRatio" xlink:label="DebtInstrumentNetLeverageRatio" xlink:title="DebtInstrumentNetLeverageRatio" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentNetLeverageRatio" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentNetLeverageRatio" order="31.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromShortTermDebt" xlink:label="ProceedsFromShortTermDebt" xlink:title="ProceedsFromShortTermDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="ProceedsFromShortTermDebt" xlink:title="definition: DebtInstrumentLineItems to ProceedsFromShortTermDebt" order="32.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit" xlink:label="LineOfCredit" xlink:title="LineOfCredit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="LineOfCredit" xlink:title="definition: DebtInstrumentLineItems to LineOfCredit" order="33.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:label="BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:title="BusinessCombinationConsiderationTransferredLiabilitiesIncurred" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="BusinessCombinationConsiderationTransferredLiabilitiesIncurred" xlink:title="definition: DebtInstrumentLineItems to BusinessCombinationConsiderationTransferredLiabilitiesIncurred" order="34.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfTermLoans" xlink:label="NumberOfTermLoans" xlink:title="NumberOfTermLoans" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DebtInstrumentLineItems" xlink:to="NumberOfTermLoans" xlink:title="definition: DebtInstrumentLineItems to NumberOfTermLoans" order="35.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="DebtInstrumentTable" xlink:title="DebtInstrumentTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DebtInstrumentLineItems" xlink:to="DebtInstrumentTable" xlink:title="definition: DebtInstrumentLineItems to DebtInstrumentTable" order="36.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="CreditFacilityAxis" xlink:title="CreditFacilityAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DebtInstrumentTable" xlink:to="CreditFacilityAxis" xlink:title="definition: DebtInstrumentTable to CreditFacilityAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="CreditFacilityDomain" xlink:title="CreditFacilityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="CreditFacilityAxis" xlink:to="CreditFacilityDomain" xlink:title="definition: CreditFacilityAxis to CreditFacilityDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="CreditFacilityDomain_2" xlink:title="CreditFacilityDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="CreditFacilityAxis" xlink:to="CreditFacilityDomain_2" xlink:title="definition: CreditFacilityAxis to CreditFacilityDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanFacilityMember" xlink:label="TermLoanFacilityMember" xlink:title="TermLoanFacilityMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="TermLoanFacilityMember" xlink:title="definition: CreditFacilityDomain to TermLoanFacilityMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanInNetherlandsDueIn2020Member" xlink:label="TermLoanInNetherlandsDueIn2020Member" xlink:title="TermLoanInNetherlandsDueIn2020Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="TermLoanInNetherlandsDueIn2020Member" xlink:title="definition: CreditFacilityDomain to TermLoanInNetherlandsDueIn2020Member" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanInNetherlandsDueIn2022Member" xlink:label="TermLoanInNetherlandsDueIn2022Member" xlink:title="TermLoanInNetherlandsDueIn2022Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="TermLoanInNetherlandsDueIn2022Member" xlink:title="definition: CreditFacilityDomain to TermLoanInNetherlandsDueIn2022Member" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanFacilityFirstAmendmentMember" xlink:label="TermLoanFacilityFirstAmendmentMember" xlink:title="TermLoanFacilityFirstAmendmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="TermLoanFacilityFirstAmendmentMember" xlink:title="definition: CreditFacilityDomain to TermLoanFacilityFirstAmendmentMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanFacilitySecondAmendmentMember" xlink:label="TermLoanFacilitySecondAmendmentMember" xlink:title="TermLoanFacilitySecondAmendmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="TermLoanFacilitySecondAmendmentMember" xlink:title="definition: CreditFacilityDomain to TermLoanFacilitySecondAmendmentMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_CommittedLoanFacilityInJapanMember" xlink:label="CommittedLoanFacilityInJapanMember" xlink:title="CommittedLoanFacilityInJapanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="CommittedLoanFacilityInJapanMember" xlink:title="definition: CreditFacilityDomain to CommittedLoanFacilityInJapanMember" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_CommittedLoanFacilityMember" xlink:label="CommittedLoanFacilityMember" xlink:title="CommittedLoanFacilityMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="CommittedLoanFacilityMember" xlink:title="definition: CreditFacilityDomain to CommittedLoanFacilityMember" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_CommittedLoanFacilityOfChinaAndJapanMember" xlink:label="CommittedLoanFacilityOfChinaAndJapanMember" xlink:title="CommittedLoanFacilityOfChinaAndJapanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="CommittedLoanFacilityOfChinaAndJapanMember" xlink:title="definition: CreditFacilityDomain to CommittedLoanFacilityOfChinaAndJapanMember" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="RevolvingCreditFacilityMember" xlink:title="RevolvingCreditFacilityMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="RevolvingCreditFacilityMember" xlink:title="definition: CreditFacilityDomain to RevolvingCreditFacilityMember" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RevolvingFacilityThirdAmendmentMember" xlink:label="RevolvingFacilityThirdAmendmentMember" xlink:title="RevolvingFacilityThirdAmendmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="RevolvingFacilityThirdAmendmentMember" xlink:title="definition: CreditFacilityDomain to RevolvingFacilityThirdAmendmentMember" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="LetterOfCreditMember" xlink:title="LetterOfCreditMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="CreditFacilityDomain" xlink:to="LetterOfCreditMember" xlink:title="definition: CreditFacilityDomain to LetterOfCreditMember" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanFacilityOneMember" xlink:label="TermLoanFacilityOneMember" xlink:title="TermLoanFacilityOneMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TermLoanFacilityMember" xlink:to="TermLoanFacilityOneMember" xlink:title="definition: TermLoanFacilityMember to TermLoanFacilityOneMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TermLoanFacilityTwoMember" xlink:label="TermLoanFacilityTwoMember" xlink:title="TermLoanFacilityTwoMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="TermLoanFacilityMember" xlink:to="TermLoanFacilityTwoMember" xlink:title="definition: TermLoanFacilityMember to TermLoanFacilityTwoMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="VariableRateAxis" xlink:title="VariableRateAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DebtInstrumentTable" xlink:to="VariableRateAxis" xlink:title="definition: DebtInstrumentTable to VariableRateAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="VariableRateDomain" xlink:title="VariableRateDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="VariableRateAxis" xlink:to="VariableRateDomain" xlink:title="definition: VariableRateAxis to VariableRateDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="VariableRateDomain_2" xlink:title="VariableRateDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="VariableRateAxis" xlink:to="VariableRateDomain_2" xlink:title="definition: VariableRateAxis to VariableRateDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="LondonInterbankOfferedRateLIBORMember" xlink:title="LondonInterbankOfferedRateLIBORMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="VariableRateDomain" xlink:to="LondonInterbankOfferedRateLIBORMember" xlink:title="definition: VariableRateDomain to LondonInterbankOfferedRateLIBORMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FloatingRateTrancheMember" xlink:label="FloatingRateTrancheMember" xlink:title="FloatingRateTrancheMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="VariableRateDomain" xlink:to="FloatingRateTrancheMember" xlink:title="definition: VariableRateDomain to FloatingRateTrancheMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FixedRateTrancheMember" xlink:label="FixedRateTrancheMember" xlink:title="FixedRateTrancheMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="VariableRateDomain" xlink:to="FixedRateTrancheMember" xlink:title="definition: VariableRateDomain to FixedRateTrancheMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EuroInterbankOfferedRateEuriborMember" xlink:label="EuroInterbankOfferedRateEuriborMember" xlink:title="EuroInterbankOfferedRateEuriborMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="VariableRateDomain" xlink:to="EuroInterbankOfferedRateEuriborMember" xlink:title="definition: VariableRateDomain to EuroInterbankOfferedRateEuriborMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="RangeAxis" xlink:title="RangeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DebtInstrumentTable" xlink:to="RangeAxis" xlink:title="definition: DebtInstrumentTable to RangeAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RangeAxis" xlink:to="RangeMember" xlink:title="definition: RangeAxis to RangeMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember_2" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RangeAxis" xlink:to="RangeMember_2" xlink:title="definition: RangeAxis to RangeMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="MinimumMember" xlink:title="MinimumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MinimumMember" xlink:title="definition: RangeMember to MinimumMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="MaximumMember" xlink:title="MaximumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MaximumMember" xlink:title="definition: RangeMember to MaximumMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="BusinessAcquisitionAxis" xlink:title="BusinessAcquisitionAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="DebtInstrumentTable" xlink:to="BusinessAcquisitionAxis" xlink:title="definition: DebtInstrumentTable to BusinessAcquisitionAxis" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain_2" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain_2" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SivomaticMember" xlink:label="SivomaticMember" xlink:title="SivomaticMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionAcquireeDomain" xlink:to="SivomaticMember" xlink:title="definition: BusinessAcquisitionAcquireeDomain to SivomaticMember" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansPensionObligationAndFundedStatusDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInBenefitObligationRollForward" xlink:label="DefinedBenefitPlanChangeInBenefitObligationRollForward" xlink:title="DefinedBenefitPlanChangeInBenefitObligationRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanChangeInBenefitObligationRollForward" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanChangeInBenefitObligationRollForward" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward" xlink:label="DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward" xlink:title="DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanChangeInFairValueOfPlanAssetsRollForward" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlanAbstract" xlink:label="DefinedBenefitPlanFundedStatusOfPlanAbstract" xlink:title="DefinedBenefitPlanFundedStatusOfPlanAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanFundedStatusOfPlanAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanFundedStatusOfPlanAbstract" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanFundedStatusOfPlan" xlink:label="DefinedBenefitPlanFundedStatusOfPlan" xlink:title="DefinedBenefitPlanFundedStatusOfPlan" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanFundedStatusOfPlan" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanFundedStatusOfPlan" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets" xlink:label="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="DefinedBenefitPlanFairValueOfPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanFairValueOfPlanAssets" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanActualReturnOnPlanAssets" xlink:label="DefinedBenefitPlanActualReturnOnPlanAssets" xlink:title="DefinedBenefitPlanActualReturnOnPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanActualReturnOnPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanActualReturnOnPlanAssets" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanContributionsByEmployer" xlink:label="DefinedBenefitPlanContributionsByEmployer" xlink:title="DefinedBenefitPlanContributionsByEmployer" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanContributionsByEmployer" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanContributionsByEmployer" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant" xlink:label="DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant" xlink:title="DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsBenefitsPaid" xlink:label="DefinedBenefitPlanPlanAssetsBenefitsPaid" xlink:title="DefinedBenefitPlanPlanAssetsBenefitsPaid" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanPlanAssetsBenefitsPaid" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanPlanAssetsBenefitsPaid" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanSettlementsPlanAssets" xlink:label="DefinedBenefitPlanSettlementsPlanAssets" xlink:title="DefinedBenefitPlanSettlementsPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanSettlementsPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanSettlementsPlanAssets" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss" xlink:label="DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss" xlink:title="DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanPlanAssetsForeignCurrencyTranslationGainLoss" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligation" xlink:label="DefinedBenefitPlanBenefitObligation" xlink:title="DefinedBenefitPlanBenefitObligation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanBenefitObligation" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanBenefitObligation" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost" xlink:label="DefinedBenefitPlanServiceCost" xlink:title="DefinedBenefitPlanServiceCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanServiceCost" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanServiceCost" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost" xlink:label="DefinedBenefitPlanInterestCost" xlink:title="DefinedBenefitPlanInterestCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanInterestCost" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanInterestCost" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanActuarialGainLoss" xlink:label="DefinedBenefitPlanActuarialGainLoss" xlink:title="DefinedBenefitPlanActuarialGainLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanActuarialGainLoss" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanActuarialGainLoss" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanBenefitObligationBenefitsPaid" xlink:label="DefinedBenefitPlanBenefitObligationBenefitsPaid" xlink:title="DefinedBenefitPlanBenefitObligationBenefitsPaid" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanBenefitObligationBenefitsPaid" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanBenefitObligationBenefitsPaid" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanSettlementsBenefitObligation" xlink:label="DefinedBenefitPlanSettlementsBenefitObligation" xlink:title="DefinedBenefitPlanSettlementsBenefitObligation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanSettlementsBenefitObligation" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanSettlementsBenefitObligation" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation" xlink:label="DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation" xlink:title="DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanForeignCurrencyExchangeRateChangesBenefitObligation" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_DefinedBenefitPlanOther" xlink:label="DefinedBenefitPlanOther" xlink:title="DefinedBenefitPlanOther" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanOther" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanOther" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="20.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansAmountsRecognizedInConsolidatedBalanceSheetDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract" xlink:label="DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract" xlink:title="DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmountsRecognizedInBalanceSheetAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities" xlink:label="PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities" xlink:title="PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to PensionAndOtherPostretirementDefinedBenefitPlansCurrentLiabilities" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent" xlink:label="PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent" xlink:title="PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInBalanceSheet" xlink:label="DefinedBenefitPlanAmountsRecognizedInBalanceSheet" xlink:title="DefinedBenefitPlanAmountsRecognizedInBalanceSheet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmountsRecognizedInBalanceSheet" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmountsRecognizedInBalanceSheet" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="5.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansAmountsRecognizedInAccumulatedOtherComprehensiveIncomeNetOfRelatedTaxEffectsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract" xlink:label="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract" xlink:title="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTaxAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedBenefitObligation" xlink:label="DefinedBenefitPlanAccumulatedBenefitObligation" xlink:title="DefinedBenefitPlanAccumulatedBenefitObligation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAccumulatedBenefitObligation" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAccumulatedBenefitObligation" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax" xlink:label="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax" xlink:title="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesAfterTax" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax" xlink:label="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax" xlink:title="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditAfterTax" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax" xlink:label="AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax" xlink:title="AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="6.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansChangesInPlanAssetsAndBenefitObligationsRecognizedInOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeAbstract" xlink:label="DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeAbstract" xlink:title="DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" xlink:label="OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" xlink:title="OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" xlink:label="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" xlink:title="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" xlink:label="OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" xlink:title="OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:label="OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:title="OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="6.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansComponentsOfNetPeriodicBenefitCostsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCostAbstract" xlink:label="DefinedBenefitPlanNetPeriodicBenefitCostAbstract" xlink:title="DefinedBenefitPlanNetPeriodicBenefitCostAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanNetPeriodicBenefitCostAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanNetPeriodicBenefitCostAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanServiceCost" xlink:label="DefinedBenefitPlanServiceCost" xlink:title="DefinedBenefitPlanServiceCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanServiceCost" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanServiceCost" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanInterestCost" xlink:label="DefinedBenefitPlanInterestCost" xlink:title="DefinedBenefitPlanInterestCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanInterestCost" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanInterestCost" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets" xlink:label="DefinedBenefitPlanExpectedReturnOnPlanAssets" xlink:title="DefinedBenefitPlanExpectedReturnOnPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedReturnOnPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedReturnOnPlanAssets" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" xlink:label="DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" xlink:title="DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmortizationOfPriorServiceCostCredit" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses" xlink:label="DefinedBenefitPlanAmortizationOfGainsLosses" xlink:title="DefinedBenefitPlanAmortizationOfGainsLosses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmortizationOfGainsLosses" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmortizationOfGainsLosses" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1" xlink:label="DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1" xlink:title="DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost" xlink:label="DefinedBenefitPlanNetPeriodicBenefitCost" xlink:title="DefinedBenefitPlanNetPeriodicBenefitCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanNetPeriodicBenefitCost" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanNetPeriodicBenefitCost" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="9.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansEstimatedAmortizationOfAmountsInOtherAccumulatedComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract" xlink:label="DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract" xlink:title="DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAmountsThatWillBeAmortizedFromAccumulatedOtherComprehensiveIncomeLossInNextFiscalYearAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear" xlink:label="DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear" xlink:title="DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedAmortizationOfGainLossNextFiscalYear" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedAmortizationNextFiscalYear" xlink:label="DefinedBenefitPlanExpectedAmortizationNextFiscalYear" xlink:title="DefinedBenefitPlanExpectedAmortizationNextFiscalYear" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedAmortizationNextFiscalYear" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedAmortizationNextFiscalYear" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="4.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansWeightedAverageAssumptionsUsedDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansWeightedAverageAssetAllocationByAssetCategoryDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:label="DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:title="DefinedBenefitPlanAssetsTargetAllocationsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAssetsTargetAllocationsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations" xlink:label="DefinedBenefitPlanWeightedAverageAssetAllocations" xlink:title="DefinedBenefitPlanWeightedAverageAssetAllocations" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanWeightedAverageAssetAllocations" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanWeightedAverageAssetAllocations" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:label="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="DefinedBenefitPlanByPlanAssetCategoriesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to DefinedBenefitPlanByPlanAssetCategoriesAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain_2" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain_2" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember" xlink:label="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="DefinedBenefitPlanEquitySecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to DefinedBenefitPlanEquitySecuritiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember" xlink:label="FixedIncomeSecuritiesMember" xlink:title="FixedIncomeSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="FixedIncomeSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to FixedIncomeSecuritiesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateMember" xlink:label="RealEstateMember" xlink:title="RealEstateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="RealEstateMember" xlink:title="definition: PlanAssetCategoriesDomain to RealEstateMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherDebtSecuritiesMember" xlink:label="OtherDebtSecuritiesMember" xlink:title="OtherDebtSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="OtherDebtSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to OtherDebtSecuritiesMember" order="4.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansFairValuesByAssetCategoryDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:label="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:title="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanInformationAboutPlanAssetsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets" xlink:label="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="DefinedBenefitPlanFairValueOfPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanFairValueOfPlanAssets" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:label="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="DefinedBenefitPlanByPlanAssetCategoriesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to DefinedBenefitPlanByPlanAssetCategoriesAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain_2" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain_2" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember" xlink:label="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="DefinedBenefitPlanEquitySecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to DefinedBenefitPlanEquitySecuritiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember" xlink:label="FixedIncomeSecuritiesMember" xlink:title="FixedIncomeSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="FixedIncomeSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to FixedIncomeSecuritiesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateMember" xlink:label="RealEstateMember" xlink:title="RealEstateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="RealEstateMember" xlink:title="definition: PlanAssetCategoriesDomain to RealEstateMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherDebtSecuritiesMember" xlink:label="OtherDebtSecuritiesMember" xlink:title="OtherDebtSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="OtherDebtSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to OtherDebtSecuritiesMember" order="4.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansDomesticAndForeignPensionPlanAssetsAndSummaryOfDefinedBenefitPensionPlanAssetsMeasuredAtFairValueDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:label="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:title="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanInformationAboutPlanAssetsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanInformationAboutPlanAssetsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanFairValueOfPlanAssets" xlink:label="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="DefinedBenefitPlanFairValueOfPlanAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanFairValueOfPlanAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanFairValueOfPlanAssets" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanSponsorLocationAxis" xlink:label="RetirementPlanSponsorLocationAxis" xlink:title="RetirementPlanSponsorLocationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanSponsorLocationAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanSponsorLocationAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain" xlink:label="RetirementPlanSponsorLocationDomain" xlink:title="RetirementPlanSponsorLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanSponsorLocationAxis" xlink:to="RetirementPlanSponsorLocationDomain" xlink:title="definition: RetirementPlanSponsorLocationAxis to RetirementPlanSponsorLocationDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanSponsorLocationDomain" xlink:label="RetirementPlanSponsorLocationDomain_2" xlink:title="RetirementPlanSponsorLocationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanSponsorLocationAxis" xlink:to="RetirementPlanSponsorLocationDomain_2" xlink:title="definition: RetirementPlanSponsorLocationAxis to RetirementPlanSponsorLocationDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DomesticPlanMember" xlink:label="DomesticPlanMember" xlink:title="DomesticPlanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanSponsorLocationDomain" xlink:to="DomesticPlanMember" xlink:title="definition: RetirementPlanSponsorLocationDomain to DomesticPlanMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignPlanMember" xlink:label="ForeignPlanMember" xlink:title="ForeignPlanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanSponsorLocationDomain" xlink:to="ForeignPlanMember" xlink:title="definition: RetirementPlanSponsorLocationDomain to ForeignPlanMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="US" xlink:title="US" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DomesticPlanMember" xlink:to="US" xlink:title="definition: DomesticPlanMember to US" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:label="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="DefinedBenefitPlanByPlanAssetCategoriesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to DefinedBenefitPlanByPlanAssetCategoriesAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain_2" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain_2" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember" xlink:label="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="DefinedBenefitPlanEquitySecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to DefinedBenefitPlanEquitySecuritiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember" xlink:label="FixedIncomeSecuritiesMember" xlink:title="FixedIncomeSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="FixedIncomeSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to FixedIncomeSecuritiesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RealEstateAndOtherMember" xlink:label="RealEstateAndOtherMember" xlink:title="RealEstateAndOtherMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="RealEstateAndOtherMember" xlink:title="definition: PlanAssetCategoriesDomain to RealEstateAndOtherMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RealEstateMember" xlink:label="RealEstateMember" xlink:title="RealEstateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RealEstateAndOtherMember" xlink:to="RealEstateMember" xlink:title="definition: RealEstateAndOtherMember to RealEstateMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherDebtSecuritiesMember" xlink:label="OtherDebtSecuritiesMember" xlink:title="OtherDebtSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RealEstateAndOtherMember" xlink:to="OtherDebtSecuritiesMember" xlink:title="definition: RealEstateAndOtherMember to OtherDebtSecuritiesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateDebtSecuritiesMember" xlink:label="CorporateDebtSecuritiesMember" xlink:title="CorporateDebtSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FixedIncomeSecuritiesMember" xlink:to="CorporateDebtSecuritiesMember" xlink:title="definition: FixedIncomeSecuritiesMember to CorporateDebtSecuritiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesUsMember" xlink:label="DefinedBenefitPlanEquitySecuritiesUsMember" xlink:title="DefinedBenefitPlanEquitySecuritiesUsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanEquitySecuritiesMember" xlink:to="DefinedBenefitPlanEquitySecuritiesUsMember" xlink:title="definition: DefinedBenefitPlanEquitySecuritiesMember to DefinedBenefitPlanEquitySecuritiesUsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesNonUsMember" xlink:label="DefinedBenefitPlanEquitySecuritiesNonUsMember" xlink:title="DefinedBenefitPlanEquitySecuritiesNonUsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanEquitySecuritiesMember" xlink:to="DefinedBenefitPlanEquitySecuritiesNonUsMember" xlink:title="definition: DefinedBenefitPlanEquitySecuritiesMember to DefinedBenefitPlanEquitySecuritiesNonUsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="FairValueByFairValueHierarchyLevelAxis" xlink:title="FairValueByFairValueHierarchyLevelAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="FairValueByFairValueHierarchyLevelAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to FairValueByFairValueHierarchyLevelAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="FairValueInputsLevel1Member" xlink:title="FairValueInputsLevel1Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel1Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel1Member" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="FairValueInputsLevel2Member" xlink:title="FairValueInputsLevel2Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel2Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel2Member" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="FairValueInputsLevel3Member" xlink:title="FairValueInputsLevel3Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel3Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel3Member" order="3.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansReconciliationOfChangesInFairValueMeasurementOfPlanAssetsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:label="FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:title="FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FairValueTransfersAbstract" xlink:label="FairValueTransfersAbstract" xlink:title="FairValueTransfersAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueTransfersAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueTransfersAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FairValueAssetsLevel3TransfersInAmount" xlink:label="FairValueAssetsLevel3TransfersInAmount" xlink:title="FairValueAssetsLevel3TransfersInAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueAssetsLevel3TransfersInAmount" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueAssetsLevel3TransfersInAmount" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FairValueAssetsLevel3TransfersOutAmount" xlink:label="FairValueAssetsLevel3TransfersOutAmount" xlink:title="FairValueAssetsLevel3TransfersOutAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueAssetsLevel3TransfersOutAmount" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueAssetsLevel3TransfersOutAmount" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:title="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements" xlink:label="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements" xlink:title="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchasesSalesIssuancesSettlements" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetActualReturnLoss" xlink:label="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetActualReturnLoss" xlink:title="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetActualReturnLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetActualReturnLoss" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetActualReturnLoss" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationGainLoss" xlink:label="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationGainLoss" xlink:title="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationGainLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationGainLoss" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetForeignCurrencyTranslationGainLoss" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="9.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="FairValueByFairValueHierarchyLevelAxis" xlink:title="FairValueByFairValueHierarchyLevelAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="FairValueByFairValueHierarchyLevelAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to FairValueByFairValueHierarchyLevelAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="FairValueByFairValueHierarchyLevelAxis" xlink:to="FairValueMeasurementsFairValueHierarchyDomain_2" xlink:title="definition: FairValueByFairValueHierarchyLevelAxis to FairValueMeasurementsFairValueHierarchyDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="FairValueInputsLevel3Member" xlink:title="FairValueInputsLevel3Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="FairValueMeasurementsFairValueHierarchyDomain" xlink:to="FairValueInputsLevel3Member" xlink:title="definition: FairValueMeasurementsFairValueHierarchyDomain to FairValueInputsLevel3Member" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansContributionsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEstimatedFutureEmployerContributionsAbstract" xlink:label="DefinedBenefitPlanEstimatedFutureEmployerContributionsAbstract" xlink:title="DefinedBenefitPlanEstimatedFutureEmployerContributionsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanEstimatedFutureEmployerContributionsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanEstimatedFutureEmployerContributionsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" xlink:label="DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" xlink:title="DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansEstimatedFutureBenefitPaymentsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract" xlink:label="DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract" xlink:title="DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanEstimatedFutureBenefitPaymentsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter" xlink:label="DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter" xlink:title="DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="8.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="RetirementPlanTypeAxis" xlink:title="RetirementPlanTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RetirementPlanTypeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RetirementPlanTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="RetirementPlanTypeDomain_2" xlink:title="RetirementPlanTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RetirementPlanTypeAxis" xlink:to="RetirementPlanTypeDomain_2" xlink:title="definition: RetirementPlanTypeAxis to RetirementPlanTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PensionPlansDefinedBenefitMember" xlink:label="PensionPlansDefinedBenefitMember" xlink:title="PensionPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="PensionPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to PensionPlansDefinedBenefitMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:label="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="OtherPostretirementBenefitPlansDefinedBenefitMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RetirementPlanTypeDomain" xlink:to="OtherPostretirementBenefitPlansDefinedBenefitMember" xlink:title="definition: RetirementPlanTypeDomain to OtherPostretirementBenefitPlansDefinedBenefitMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansInvestmentStrategiesDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems" xlink:label="DefinedBenefitPlanDisclosureLineItems" xlink:title="DefinedBenefitPlanDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:label="DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:title="DefinedBenefitPlanAssetsTargetAllocationsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanAssetsTargetAllocationsAbstract" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanAssetsTargetAllocationsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AverageRateOfReturnOnAssets" xlink:label="AverageRateOfReturnOnAssets" xlink:title="AverageRateOfReturnOnAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="AverageRateOfReturnOnAssets" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to AverageRateOfReturnOnAssets" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage" xlink:label="DefinedBenefitPlanPlanAssetsTargetAllocationPercentage" xlink:title="DefinedBenefitPlanPlanAssetsTargetAllocationPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="DefinedBenefitPlanPlanAssetsTargetAllocationPercentage" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to DefinedBenefitPlanPlanAssetsTargetAllocationPercentage" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:label="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="ScheduleOfDefinedBenefitPlansDisclosuresTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="DefinedBenefitPlanDisclosureLineItems" xlink:to="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:title="definition: DefinedBenefitPlanDisclosureLineItems to ScheduleOfDefinedBenefitPlansDisclosuresTable" order="4.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:label="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="DefinedBenefitPlanByPlanAssetCategoriesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to DefinedBenefitPlanByPlanAssetCategoriesAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanAssetCategoriesDomain" xlink:label="PlanAssetCategoriesDomain_2" xlink:title="PlanAssetCategoriesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DefinedBenefitPlanByPlanAssetCategoriesAxis" xlink:to="PlanAssetCategoriesDomain_2" xlink:title="definition: DefinedBenefitPlanByPlanAssetCategoriesAxis to PlanAssetCategoriesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DefinedBenefitPlanEquitySecuritiesMember" xlink:label="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="DefinedBenefitPlanEquitySecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="DefinedBenefitPlanEquitySecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to DefinedBenefitPlanEquitySecuritiesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember" xlink:label="FixedIncomeSecuritiesMember" xlink:title="FixedIncomeSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="FixedIncomeSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to FixedIncomeSecuritiesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherDebtSecuritiesMember" xlink:label="OtherDebtSecuritiesMember" xlink:title="OtherDebtSecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="PlanAssetCategoriesDomain" xlink:to="OtherDebtSecuritiesMember" xlink:title="definition: PlanAssetCategoriesDomain to OtherDebtSecuritiesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="RangeAxis" xlink:title="RangeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfDefinedBenefitPlansDisclosuresTable" xlink:to="RangeAxis" xlink:title="definition: ScheduleOfDefinedBenefitPlansDisclosuresTable to RangeAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="RangeAxis" xlink:to="RangeMember" xlink:title="definition: RangeAxis to RangeMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="RangeMember_2" xlink:title="RangeMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="RangeAxis" xlink:to="RangeMember_2" xlink:title="definition: RangeAxis to RangeMember_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="MinimumMember" xlink:title="MinimumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MinimumMember" xlink:title="definition: RangeMember to MinimumMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="MaximumMember" xlink:title="MaximumMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RangeMember" xlink:to="MaximumMember" xlink:title="definition: RangeMember to MaximumMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/BenefitPlansSavingsAndInvestmentPlansDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/LitigationDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SiteContingencyLineItems" xlink:label="SiteContingencyLineItems" xlink:title="SiteContingencyLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EnvironmentalRemediationObligationsAbstract" xlink:label="EnvironmentalRemediationObligationsAbstract" xlink:title="EnvironmentalRemediationObligationsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="EnvironmentalRemediationObligationsAbstract" xlink:title="definition: SiteContingencyLineItems to EnvironmentalRemediationObligationsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SiteContingencyNameOfSite" xlink:label="SiteContingencyNameOfSite" xlink:title="SiteContingencyNameOfSite" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="SiteContingencyNameOfSite" xlink:title="definition: SiteContingencyLineItems to SiteContingencyNameOfSite" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ConsentDecreeSettlement" xlink:label="ConsentDecreeSettlement" xlink:title="ConsentDecreeSettlement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="ConsentDecreeSettlement" xlink:title="definition: SiteContingencyLineItems to ConsentDecreeSettlement" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccrualForEnvironmentalLossContingencies" xlink:label="AccrualForEnvironmentalLossContingencies" xlink:title="AccrualForEnvironmentalLossContingencies" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="AccrualForEnvironmentalLossContingencies" xlink:title="definition: SiteContingencyLineItems to AccrualForEnvironmentalLossContingencies" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EstimatedCostOfWastewaterTreatmentUpgradesLowerRange" xlink:label="EstimatedCostOfWastewaterTreatmentUpgradesLowerRange" xlink:title="EstimatedCostOfWastewaterTreatmentUpgradesLowerRange" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="EstimatedCostOfWastewaterTreatmentUpgradesLowerRange" xlink:title="definition: SiteContingencyLineItems to EstimatedCostOfWastewaterTreatmentUpgradesLowerRange" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EstimatedCostOfWastewaterTreatmentUpgradesUpperRange" xlink:label="EstimatedCostOfWastewaterTreatmentUpgradesUpperRange" xlink:title="EstimatedCostOfWastewaterTreatmentUpgradesUpperRange" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SiteContingencyLineItems" xlink:to="EstimatedCostOfWastewaterTreatmentUpgradesUpperRange" xlink:title="definition: SiteContingencyLineItems to EstimatedCostOfWastewaterTreatmentUpgradesUpperRange" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SiteContingencyTable" xlink:label="SiteContingencyTable" xlink:title="SiteContingencyTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="SiteContingencyLineItems" xlink:to="SiteContingencyTable" xlink:title="definition: SiteContingencyLineItems to SiteContingencyTable" order="7.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EnvironmentalRemediationSiteAxis" xlink:label="EnvironmentalRemediationSiteAxis" xlink:title="EnvironmentalRemediationSiteAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="SiteContingencyTable" xlink:to="EnvironmentalRemediationSiteAxis" xlink:title="definition: SiteContingencyTable to EnvironmentalRemediationSiteAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EnvironmentalRemediationSiteDomain" xlink:label="EnvironmentalRemediationSiteDomain" xlink:title="EnvironmentalRemediationSiteDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="EnvironmentalRemediationSiteAxis" xlink:to="EnvironmentalRemediationSiteDomain" xlink:title="definition: EnvironmentalRemediationSiteAxis to EnvironmentalRemediationSiteDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EnvironmentalRemediationSiteDomain" xlink:label="EnvironmentalRemediationSiteDomain_2" xlink:title="EnvironmentalRemediationSiteDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="EnvironmentalRemediationSiteAxis" xlink:to="EnvironmentalRemediationSiteDomain_2" xlink:title="definition: EnvironmentalRemediationSiteAxis to EnvironmentalRemediationSiteDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AdministrativeConsentOrderForContaminationAssociatedWithHistoricUseOfPcbsMember" xlink:label="AdministrativeConsentOrderForContaminationAssociatedWithHistoricUseOfPcbsMember" xlink:title="AdministrativeConsentOrderForContaminationAssociatedWithHistoricUseOfPcbsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EnvironmentalRemediationSiteDomain" xlink:to="AdministrativeConsentOrderForContaminationAssociatedWithHistoricUseOfPcbsMember" xlink:title="definition: EnvironmentalRemediationSiteDomain to AdministrativeConsentOrderForContaminationAssociatedWithHistoricUseOfPcbsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AdministrativeConsentOrderForInstallationOfGroundwaterContaminationSystemMember" xlink:label="AdministrativeConsentOrderForInstallationOfGroundwaterContaminationSystemMember" xlink:title="AdministrativeConsentOrderForInstallationOfGroundwaterContaminationSystemMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EnvironmentalRemediationSiteDomain" xlink:to="AdministrativeConsentOrderForInstallationOfGroundwaterContaminationSystemMember" xlink:title="definition: EnvironmentalRemediationSiteDomain to AdministrativeConsentOrderForInstallationOfGroundwaterContaminationSystemMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingenciesLineItems" xlink:label="LossContingenciesLineItems" xlink:title="LossContingenciesLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyInformationAboutLitigationMattersAbstract" xlink:label="LossContingencyInformationAboutLitigationMattersAbstract" xlink:title="LossContingencyInformationAboutLitigationMattersAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyInformationAboutLitigationMattersAbstract" xlink:title="definition: LossContingenciesLineItems to LossContingencyInformationAboutLitigationMattersAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyPendingClaimsNumber" xlink:label="LossContingencyPendingClaimsNumber" xlink:title="LossContingencyPendingClaimsNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyPendingClaimsNumber" xlink:title="definition: LossContingenciesLineItems to LossContingencyPendingClaimsNumber" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_LossContingencyClaimsDismissedCumulativeNumber" xlink:label="LossContingencyClaimsDismissedCumulativeNumber" xlink:title="LossContingencyClaimsDismissedCumulativeNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyClaimsDismissedCumulativeNumber" xlink:title="definition: LossContingenciesLineItems to LossContingencyClaimsDismissedCumulativeNumber" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyNewClaimsFiledNumber" xlink:label="LossContingencyNewClaimsFiledNumber" xlink:title="LossContingencyNewClaimsFiledNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyNewClaimsFiledNumber" xlink:title="definition: LossContingenciesLineItems to LossContingencyNewClaimsFiledNumber" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LitigationSettlementExpense" xlink:label="LitigationSettlementExpense" xlink:title="LitigationSettlementExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LitigationSettlementExpense" xlink:title="definition: LossContingenciesLineItems to LitigationSettlementExpense" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyClaimsDismissedNumber" xlink:label="LossContingencyClaimsDismissedNumber" xlink:title="LossContingencyClaimsDismissedNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyClaimsDismissedNumber" xlink:title="definition: LossContingenciesLineItems to LossContingencyClaimsDismissedNumber" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyClaimsSettledNumber" xlink:label="LossContingencyClaimsSettledNumber" xlink:title="LossContingencyClaimsSettledNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="LossContingencyClaimsSettledNumber" xlink:title="definition: LossContingenciesLineItems to LossContingencyClaimsSettledNumber" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfCasesClaimLiability" xlink:label="NumberOfCasesClaimLiability" xlink:title="NumberOfCasesClaimLiability" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="NumberOfCasesClaimLiability" xlink:title="definition: LossContingenciesLineItems to NumberOfCasesClaimLiability" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfAllegeLiability" xlink:label="NumberOfAllegeLiability" xlink:title="NumberOfAllegeLiability" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="NumberOfAllegeLiability" xlink:title="definition: LossContingenciesLineItems to NumberOfAllegeLiability" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfCasesWithNoAllegedExposureDate" xlink:label="NumberOfCasesWithNoAllegedExposureDate" xlink:title="NumberOfCasesWithNoAllegedExposureDate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="NumberOfCasesWithNoAllegedExposureDate" xlink:title="definition: LossContingenciesLineItems to NumberOfCasesWithNoAllegedExposureDate" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfRemainingNonAMCOLCasesWhereAllegedExposureIsAfterCompanySIPO" xlink:label="NumberOfRemainingNonAMCOLCasesWhereAllegedExposureIsAfterCompanySIPO" xlink:title="NumberOfRemainingNonAMCOLCasesWhereAllegedExposureIsAfterCompanySIPO" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="NumberOfRemainingNonAMCOLCasesWhereAllegedExposureIsAfterCompanySIPO" xlink:title="definition: LossContingenciesLineItems to NumberOfRemainingNonAMCOLCasesWhereAllegedExposureIsAfterCompanySIPO" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_NumberOfRemainingCasesThatInvolveAMCOLOnlyNoIndemnity" xlink:label="NumberOfRemainingCasesThatInvolveAMCOLOnlyNoIndemnity" xlink:title="NumberOfRemainingCasesThatInvolveAMCOLOnlyNoIndemnity" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingenciesLineItems" xlink:to="NumberOfRemainingCasesThatInvolveAMCOLOnlyNoIndemnity" xlink:title="definition: LossContingenciesLineItems to NumberOfRemainingCasesThatInvolveAMCOLOnlyNoIndemnity" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingenciesTable" xlink:label="LossContingenciesTable" xlink:title="LossContingenciesTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="LossContingenciesLineItems" xlink:to="LossContingenciesTable" xlink:title="definition: LossContingenciesLineItems to LossContingenciesTable" order="13.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis" xlink:label="LossContingenciesByNatureOfContingencyAxis" xlink:title="LossContingenciesByNatureOfContingencyAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="LossContingenciesTable" xlink:to="LossContingenciesByNatureOfContingencyAxis" xlink:title="definition: LossContingenciesTable to LossContingenciesByNatureOfContingencyAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="LossContingencyNatureDomain" xlink:title="LossContingencyNatureDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="LossContingenciesByNatureOfContingencyAxis" xlink:to="LossContingencyNatureDomain" xlink:title="definition: LossContingenciesByNatureOfContingencyAxis to LossContingencyNatureDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="LossContingencyNatureDomain_2" xlink:title="LossContingencyNatureDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="LossContingenciesByNatureOfContingencyAxis" xlink:to="LossContingencyNatureDomain_2" xlink:title="definition: LossContingenciesByNatureOfContingencyAxis to LossContingencyNatureDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SilicaCasesMember" xlink:label="SilicaCasesMember" xlink:title="SilicaCasesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingencyNatureDomain" xlink:to="SilicaCasesMember" xlink:title="definition: LossContingencyNatureDomain to SilicaCasesMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AsbestosCasesMember" xlink:label="AsbestosCasesMember" xlink:title="AsbestosCasesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="LossContingencyNatureDomain" xlink:to="AsbestosCasesMember" xlink:title="definition: LossContingencyNatureDomain to AsbestosCasesMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="BusinessAcquisitionAxis" xlink:title="BusinessAcquisitionAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="LossContingenciesTable" xlink:to="BusinessAcquisitionAxis" xlink:title="definition: LossContingenciesTable to BusinessAcquisitionAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="BusinessAcquisitionAcquireeDomain_2" xlink:title="BusinessAcquisitionAcquireeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="BusinessAcquisitionAxis" xlink:to="BusinessAcquisitionAcquireeDomain_2" xlink:title="definition: BusinessAcquisitionAxis to BusinessAcquisitionAcquireeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_AmcolInternationalCorporationMember" xlink:label="AmcolInternationalCorporationMember" xlink:title="AmcolInternationalCorporationMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="BusinessAcquisitionAcquireeDomain" xlink:to="AmcolInternationalCorporationMember" xlink:title="definition: BusinessAcquisitionAcquireeDomain to AmcolInternationalCorporationMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="SubsequentEventTypeAxis" xlink:title="SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="LossContingenciesTable" xlink:to="SubsequentEventTypeAxis" xlink:title="definition: LossContingenciesTable to SubsequentEventTypeAxis" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="SubsequentEventTypeDomain" xlink:title="SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="SubsequentEventTypeAxis" xlink:to="SubsequentEventTypeDomain" xlink:title="definition: SubsequentEventTypeAxis to SubsequentEventTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="SubsequentEventTypeDomain_2" xlink:title="SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="SubsequentEventTypeAxis" xlink:to="SubsequentEventTypeDomain_2" xlink:title="definition: SubsequentEventTypeAxis to SubsequentEventTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="SubsequentEventMember" xlink:title="SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventTypeDomain" xlink:to="SubsequentEventMember" xlink:title="definition: SubsequentEventTypeDomain to SubsequentEventMember" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockholdersEquityCapitalStockAndCashDividendsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="SubsequentEventLineItems" xlink:title="SubsequentEventLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsCashAbstract" xlink:label="DividendsCashAbstract" xlink:title="DividendsCashAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventLineItems" xlink:to="DividendsCashAbstract" xlink:title="definition: SubsequentEventLineItems to DividendsCashAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsOfDividendsCommonStock" xlink:label="PaymentsOfDividendsCommonStock" xlink:title="PaymentsOfDividendsCommonStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventLineItems" xlink:to="PaymentsOfDividendsCommonStock" xlink:title="definition: SubsequentEventLineItems to PaymentsOfDividendsCommonStock" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareCashPaid" xlink:label="CommonStockDividendsPerShareCashPaid" xlink:title="CommonStockDividendsPerShareCashPaid" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventLineItems" xlink:to="CommonStockDividendsPerShareCashPaid" xlink:title="definition: SubsequentEventLineItems to CommonStockDividendsPerShareCashPaid" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsPayableCurrentAndNoncurrent" xlink:label="DividendsPayableCurrentAndNoncurrent" xlink:title="DividendsPayableCurrentAndNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventLineItems" xlink:to="DividendsPayableCurrentAndNoncurrent" xlink:title="definition: SubsequentEventLineItems to DividendsPayableCurrentAndNoncurrent" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsPayableAmountPerShare" xlink:label="DividendsPayableAmountPerShare" xlink:title="DividendsPayableAmountPerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventLineItems" xlink:to="DividendsPayableAmountPerShare" xlink:title="definition: SubsequentEventLineItems to DividendsPayableAmountPerShare" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="SubsequentEventTable" xlink:title="SubsequentEventTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="SubsequentEventLineItems" xlink:to="SubsequentEventTable" xlink:title="definition: SubsequentEventLineItems to SubsequentEventTable" order="6.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="SubsequentEventTypeAxis" xlink:title="SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="SubsequentEventTable" xlink:to="SubsequentEventTypeAxis" xlink:title="definition: SubsequentEventTable to SubsequentEventTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="SubsequentEventTypeDomain" xlink:title="SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="SubsequentEventTypeAxis" xlink:to="SubsequentEventTypeDomain" xlink:title="definition: SubsequentEventTypeAxis to SubsequentEventTypeDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="SubsequentEventTypeDomain_2" xlink:title="SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="SubsequentEventTypeAxis" xlink:to="SubsequentEventTypeDomain_2" xlink:title="definition: SubsequentEventTypeAxis to SubsequentEventTypeDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="SubsequentEventMember" xlink:title="SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SubsequentEventTypeDomain" xlink:to="SubsequentEventMember" xlink:title="definition: SubsequentEventTypeDomain to SubsequentEventMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsAxis" xlink:label="DividendsAxis" xlink:title="DividendsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="SubsequentEventTable" xlink:to="DividendsAxis" xlink:title="definition: SubsequentEventTable to DividendsAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsDomain" xlink:label="DividendsDomain" xlink:title="DividendsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="DividendsAxis" xlink:to="DividendsDomain" xlink:title="definition: DividendsAxis to DividendsDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsDomain" xlink:label="DividendsDomain_2" xlink:title="DividendsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="DividendsAxis" xlink:to="DividendsDomain_2" xlink:title="definition: DividendsAxis to DividendsDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendDeclaredMember" xlink:label="DividendDeclaredMember" xlink:title="DividendDeclaredMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="DividendsDomain" xlink:to="DividendDeclaredMember" xlink:title="definition: DividendsDomain to DividendDeclaredMember" order="1.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/StockholdersEquityStockAwardAndIncentivePlanDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardAdditionalGeneralDisclosuresAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfSharesRollForward" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAdditionalDisclosuresAbstract" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantRollForward" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantGrantsInPeriod" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExercisedOrVestedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExercisedOrVestedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExercisedOrVestedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExercisedOrVestedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExercisedOrVestedInPeriod" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantForfeitedInPeriod" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" order="14.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" order="15.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" order="16.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" order="17.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" order="18.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedWeightedAverageGrantDateFairValue" order="19.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" order="20.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" order="21.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" order="22.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" order="23.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" order="24.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:title="StockIssuedDuringPeriodSharesStockOptionsExercised" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to StockIssuedDuringPeriodSharesStockOptionsExercised" order="25.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" order="26.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod" order="27.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized" order="28.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:title="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" order="29.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:title="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" order="30.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:title="definition: ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems to ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" order="31.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="AwardTypeAxis" xlink:title="AwardTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="AwardTypeAxis" xlink:title="definition: ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable to AwardTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="AwardTypeAxis" xlink:to="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" xlink:title="definition: AwardTypeAxis to ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockOptionMember" xlink:label="StockOptionMember" xlink:title="StockOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="StockOptionMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to StockOptionMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="RestrictedStockMember" xlink:title="RestrictedStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="RestrictedStockMember" xlink:title="definition: ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain to RestrictedStockMember" order="2.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccumulatedOtherComprehensiveIncomeLossDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/AccountingForAssetRetirementObligationsDetails" />
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SegmentAndRelatedInformationReportableSegmentsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="SegmentReportingInformationLineItems" xlink:title="SegmentReportingInformationLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:label="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:title="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:title="definition: SegmentReportingInformationLineItems to SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract" xlink:label="ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract" xlink:title="ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract" xlink:title="definition: SegmentReportingInformationLineItems to ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedAbstract" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts" xlink:label="BusinessCombinationAcquisitionRelatedCosts" xlink:title="BusinessCombinationAcquisitionRelatedCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="BusinessCombinationAcquisitionRelatedCosts" xlink:title="definition: SegmentReportingInformationLineItems to BusinessCombinationAcquisitionRelatedCosts" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_UnallocatedCorporateExpenses" xlink:label="UnallocatedCorporateExpenses" xlink:title="UnallocatedCorporateExpenses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="UnallocatedCorporateExpenses" xlink:title="definition: SegmentReportingInformationLineItems to UnallocatedCorporateExpenses" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="OperatingIncomeLoss" xlink:title="OperatingIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="OperatingIncomeLoss" xlink:title="definition: SegmentReportingInformationLineItems to OperatingIncomeLoss" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="NonoperatingIncomeExpense" xlink:title="NonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="NonoperatingIncomeExpense" xlink:title="definition: SegmentReportingInformationLineItems to NonoperatingIncomeExpense" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:title="definition: SegmentReportingInformationLineItems to IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: SegmentReportingInformationLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="DepreciationDepletionAndAmortization" xlink:title="DepreciationDepletionAndAmortization" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="DepreciationDepletionAndAmortization" xlink:title="definition: SegmentReportingInformationLineItems to DepreciationDepletionAndAmortization" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Assets" xlink:label="Assets" xlink:title="Assets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="Assets" xlink:title="definition: SegmentReportingInformationLineItems to Assets" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="PaymentsToAcquirePropertyPlantAndEquipment" xlink:title="PaymentsToAcquirePropertyPlantAndEquipment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentReportingInformationLineItems" xlink:to="PaymentsToAcquirePropertyPlantAndEquipment" xlink:title="definition: SegmentReportingInformationLineItems to PaymentsToAcquirePropertyPlantAndEquipment" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="ScheduleOfSegmentReportingInformationBySegmentTable" xlink:title="ScheduleOfSegmentReportingInformationBySegmentTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="SegmentReportingInformationLineItems" xlink:to="ScheduleOfSegmentReportingInformationBySegmentTable" xlink:title="definition: SegmentReportingInformationLineItems to ScheduleOfSegmentReportingInformationBySegmentTable" order="12.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="ConsolidationItemsAxis" xlink:title="ConsolidationItemsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="ConsolidationItemsAxis" xlink:title="definition: ScheduleOfSegmentReportingInformationBySegmentTable to ConsolidationItemsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="ConsolidationItemsDomain" xlink:title="ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ConsolidationItemsAxis" xlink:to="ConsolidationItemsDomain" xlink:title="definition: ConsolidationItemsAxis to ConsolidationItemsDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="ConsolidationItemsDomain_2" xlink:title="ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ConsolidationItemsAxis" xlink:to="ConsolidationItemsDomain_2" xlink:title="definition: ConsolidationItemsAxis to ConsolidationItemsDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="OperatingSegmentsMember" xlink:title="OperatingSegmentsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ConsolidationItemsDomain" xlink:to="OperatingSegmentsMember" xlink:title="definition: ConsolidationItemsDomain to OperatingSegmentsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateNonSegmentMember" xlink:label="CorporateNonSegmentMember" xlink:title="CorporateNonSegmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ConsolidationItemsDomain" xlink:to="CorporateNonSegmentMember" xlink:title="definition: ConsolidationItemsDomain to CorporateNonSegmentMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="StatementBusinessSegmentsAxis" xlink:title="StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="StatementBusinessSegmentsAxis" xlink:title="definition: ScheduleOfSegmentReportingInformationBySegmentTable to StatementBusinessSegmentsAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain_2" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain_2" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PerformanceMaterialsMember" xlink:label="PerformanceMaterialsMember" xlink:title="PerformanceMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="PerformanceMaterialsMember" xlink:title="definition: SegmentDomain to PerformanceMaterialsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyMineralsMember" xlink:label="SpecialtyMineralsMember" xlink:title="SpecialtyMineralsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="SpecialtyMineralsMember" xlink:title="definition: SegmentDomain to SpecialtyMineralsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoriesMember" xlink:label="RefractoriesMember" xlink:title="RefractoriesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="RefractoriesMember" xlink:title="definition: SegmentDomain to RefractoriesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnergyServicesMember" xlink:label="EnergyServicesMember" xlink:title="EnergyServicesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="EnergyServicesMember" xlink:title="definition: SegmentDomain to EnergyServicesMember" order="4.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SegmentAndRelatedInformationSalesByRegionCategoryDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:label="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:title="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:label="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:title="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:to="SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" xlink:title="definition: RevenuesFromExternalCustomersAndLongLivedAssetsLineItems to SegmentReportingDisclosureOfEntitysReportableSegmentsAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: RevenuesFromExternalCustomersAndLongLivedAssetsLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncurrentAssets" xlink:label="NoncurrentAssets" xlink:title="NoncurrentAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:to="NoncurrentAssets" xlink:title="definition: RevenuesFromExternalCustomersAndLongLivedAssetsLineItems to NoncurrentAssets" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" xlink:label="ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" xlink:title="ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="RevenuesFromExternalCustomersAndLongLivedAssetsLineItems" xlink:to="ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" xlink:title="definition: RevenuesFromExternalCustomersAndLongLivedAssetsLineItems to ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" order="4.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="ConsolidationItemsAxis" xlink:title="ConsolidationItemsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" xlink:to="ConsolidationItemsAxis" xlink:title="definition: ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable to ConsolidationItemsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="ConsolidationItemsDomain" xlink:title="ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ConsolidationItemsAxis" xlink:to="ConsolidationItemsDomain" xlink:title="definition: ConsolidationItemsAxis to ConsolidationItemsDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="ConsolidationItemsDomain_2" xlink:title="ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ConsolidationItemsAxis" xlink:to="ConsolidationItemsDomain_2" xlink:title="definition: ConsolidationItemsAxis to ConsolidationItemsDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ReportableGeographicalComponentsMember" xlink:label="ReportableGeographicalComponentsMember" xlink:title="ReportableGeographicalComponentsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ConsolidationItemsDomain" xlink:to="ReportableGeographicalComponentsMember" xlink:title="definition: ConsolidationItemsDomain to ReportableGeographicalComponentsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="StatementGeographicalAxis" xlink:title="StatementGeographicalAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable" xlink:to="StatementGeographicalAxis" xlink:title="definition: ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable to StatementGeographicalAxis" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="SegmentGeographicalDomain" xlink:title="SegmentGeographicalDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementGeographicalAxis" xlink:to="SegmentGeographicalDomain" xlink:title="definition: StatementGeographicalAxis to SegmentGeographicalDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="SegmentGeographicalDomain_2" xlink:title="SegmentGeographicalDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementGeographicalAxis" xlink:to="SegmentGeographicalDomain_2" xlink:title="definition: StatementGeographicalAxis to SegmentGeographicalDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="US" xlink:title="US" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentGeographicalDomain" xlink:to="US" xlink:title="definition: SegmentGeographicalDomain to US" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_CanadaLatinAmericaMember" xlink:label="CanadaLatinAmericaMember" xlink:title="CanadaLatinAmericaMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentGeographicalDomain" xlink:to="CanadaLatinAmericaMember" xlink:title="definition: SegmentGeographicalDomain to CanadaLatinAmericaMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EuropeAfricaMember" xlink:label="EuropeAfricaMember" xlink:title="EuropeAfricaMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentGeographicalDomain" xlink:to="EuropeAfricaMember" xlink:title="definition: SegmentGeographicalDomain to EuropeAfricaMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_AsiaMember" xlink:label="AsiaMember" xlink:title="AsiaMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentGeographicalDomain" xlink:to="AsiaMember" xlink:title="definition: SegmentGeographicalDomain to AsiaMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TotalInternationalMember" xlink:label="TotalInternationalMember" xlink:title="TotalInternationalMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentGeographicalDomain" xlink:to="TotalInternationalMember" xlink:title="definition: SegmentGeographicalDomain to TotalInternationalMember" order="5.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/SegmentAndRelatedInformationSalesByProductCategoryDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:label="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:title="EntityWideInformationRevenueFromExternalCustomerLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="RevenuesAbstract" xlink:title="RevenuesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="RevenuesAbstract" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to RevenuesAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:label="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:title="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" order="3.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="ProductOrServiceAxis" xlink:title="ProductOrServiceAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="ProductOrServiceAxis" xlink:title="definition: ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable to ProductOrServiceAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="ProductsAndServicesDomain_2" xlink:title="ProductsAndServicesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ProductOrServiceAxis" xlink:to="ProductsAndServicesDomain_2" xlink:title="definition: ProductOrServiceAxis to ProductsAndServicesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MetalcastingMember" xlink:label="MetalcastingMember" xlink:title="MetalcastingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MetalcastingMember" xlink:title="definition: ProductsAndServicesDomain to MetalcastingMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_HouseholdPersonalCareAndSpecialtyProductsMember" xlink:label="HouseholdPersonalCareAndSpecialtyProductsMember" xlink:title="HouseholdPersonalCareAndSpecialtyProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="HouseholdPersonalCareAndSpecialtyProductsMember" xlink:title="definition: ProductsAndServicesDomain to HouseholdPersonalCareAndSpecialtyProductsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnvironmentalProductsMember" xlink:label="EnvironmentalProductsMember" xlink:title="EnvironmentalProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="EnvironmentalProductsMember" xlink:title="definition: ProductsAndServicesDomain to EnvironmentalProductsMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_BuildingMaterialsMember" xlink:label="BuildingMaterialsMember" xlink:title="BuildingMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="BuildingMaterialsMember" xlink:title="definition: ProductsAndServicesDomain to BuildingMaterialsMember" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MineralMember" xlink:label="MineralMember" xlink:title="MineralMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MineralMember" xlink:title="definition: ProductsAndServicesDomain to MineralMember" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PaperPccMember" xlink:label="PaperPccMember" xlink:title="PaperPccMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="PaperPccMember" xlink:title="definition: ProductsAndServicesDomain to PaperPccMember" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyPccMember" xlink:label="SpecialtyPccMember" xlink:title="SpecialtyPccMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="SpecialtyPccMember" xlink:title="definition: ProductsAndServicesDomain to SpecialtyPccMember" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_GroundCalciumCarbonateMember" xlink:label="GroundCalciumCarbonateMember" xlink:title="GroundCalciumCarbonateMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="GroundCalciumCarbonateMember" xlink:title="definition: ProductsAndServicesDomain to GroundCalciumCarbonateMember" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_TalcMember" xlink:label="TalcMember" xlink:title="TalcMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="TalcMember" xlink:title="definition: ProductsAndServicesDomain to TalcMember" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoryProductsMember" xlink:label="RefractoryProductsMember" xlink:title="RefractoryProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="RefractoryProductsMember" xlink:title="definition: ProductsAndServicesDomain to RefractoryProductsMember" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MetallurgicalProductsMember" xlink:label="MetallurgicalProductsMember" xlink:title="MetallurgicalProductsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="MetallurgicalProductsMember" xlink:title="definition: ProductsAndServicesDomain to MetallurgicalProductsMember" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnergyServicesMember" xlink:label="EnergyServicesMember" xlink:title="EnergyServicesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ProductsAndServicesDomain" xlink:to="EnergyServicesMember" xlink:title="definition: ProductsAndServicesDomain to EnergyServicesMember" order="12.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/QuarterlyFinancialDataUnauditedDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:label="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:title="EntityWideInformationRevenueFromExternalCustomerLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="RevenuesAbstract" xlink:title="RevenuesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="RevenuesAbstract" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to RevenuesAbstract" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="EarningsPerShareBasic" xlink:title="EarningsPerShareBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="EarningsPerShareBasic" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to EarningsPerShareBasic" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="EarningsPerShareDiluted" xlink:title="EarningsPerShareDiluted" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="EarningsPerShareDiluted" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to EarningsPerShareDiluted" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MarketPriceRangePerShareOfCommonStockAbstract" xlink:label="MarketPriceRangePerShareOfCommonStockAbstract" xlink:title="MarketPriceRangePerShareOfCommonStockAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="MarketPriceRangePerShareOfCommonStockAbstract" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to MarketPriceRangePerShareOfCommonStockAbstract" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareCashPaid" xlink:label="CommonStockDividendsPerShareCashPaid" xlink:title="CommonStockDividendsPerShareCashPaid" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="CommonStockDividendsPerShareCashPaid" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to CommonStockDividendsPerShareCashPaid" order="5.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MarketPriceOfCommonStockHigh" xlink:label="MarketPriceOfCommonStockHigh" xlink:title="MarketPriceOfCommonStockHigh" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="MarketPriceOfCommonStockHigh" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to MarketPriceOfCommonStockHigh" order="6.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MarketPriceOfCommonStockLow" xlink:label="MarketPriceOfCommonStockLow" xlink:title="MarketPriceOfCommonStockLow" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="MarketPriceOfCommonStockLow" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to MarketPriceOfCommonStockLow" order="7.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_MarketPriceOfCommonStockClose" xlink:label="MarketPriceOfCommonStockClose" xlink:title="MarketPriceOfCommonStockClose" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="MarketPriceOfCommonStockClose" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to MarketPriceOfCommonStockClose" order="8.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="RevenueFromContractWithCustomerExcludingAssessedTax" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to RevenueFromContractWithCustomerExcludingAssessedTax" order="9.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GrossProfit" xlink:label="GrossProfit" xlink:title="GrossProfit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="GrossProfit" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to GrossProfit" order="10.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="OperatingIncomeLoss" xlink:title="OperatingIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="OperatingIncomeLoss" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to OperatingIncomeLoss" order="11.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="ProfitLoss" xlink:title="ProfitLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="ProfitLoss" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to ProfitLoss" order="12.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="NetIncomeLoss" xlink:title="NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="NetIncomeLoss" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to NetIncomeLoss" order="13.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:label="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:title="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="EntityWideInformationRevenueFromExternalCustomerLineItems" xlink:to="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:title="definition: EntityWideInformationRevenueFromExternalCustomerLineItems to ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" order="14.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="StatementBusinessSegmentsAxis" xlink:title="StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable" xlink:to="StatementBusinessSegmentsAxis" xlink:title="definition: ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable to StatementBusinessSegmentsAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="SegmentDomain_2" xlink:title="SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="StatementBusinessSegmentsAxis" xlink:to="SegmentDomain_2" xlink:title="definition: StatementBusinessSegmentsAxis to SegmentDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_PerformanceMaterialsMember" xlink:label="PerformanceMaterialsMember" xlink:title="PerformanceMaterialsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="PerformanceMaterialsMember" xlink:title="definition: SegmentDomain to PerformanceMaterialsMember" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_SpecialtyMineralsMember" xlink:label="SpecialtyMineralsMember" xlink:title="SpecialtyMineralsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="SpecialtyMineralsMember" xlink:title="definition: SegmentDomain to SpecialtyMineralsMember" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_RefractoriesMember" xlink:label="RefractoriesMember" xlink:title="RefractoriesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="RefractoriesMember" xlink:title="definition: SegmentDomain to RefractoriesMember" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="mtx-20191231.xsd#mtx_EnergyServicesMember" xlink:label="EnergyServicesMember" xlink:title="EnergyServicesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="SegmentDomain" xlink:to="EnergyServicesMember" xlink:title="definition: SegmentDomain to EnergyServicesMember" order="4.0" />
  </link:definitionLink>
  <link:definitionLink xlink:type="extended" xlink:role="http://mineralstech.com/role/ScheduleIivaluationAndQualifyingAccountsDetails">
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems" xlink:label="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:title="ValuationAndQualifyingAccountsDisclosureLineItems" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward" xlink:label="MovementInValuationAllowancesAndReservesRollForward" xlink:title="MovementInValuationAllowancesAndReservesRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="MovementInValuationAllowancesAndReservesRollForward" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureLineItems to MovementInValuationAllowancesAndReservesRollForward" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance" xlink:label="ValuationAllowancesAndReservesBalance" xlink:title="ValuationAllowancesAndReservesBalance" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="ValuationAllowancesAndReservesBalance" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureLineItems to ValuationAllowancesAndReservesBalance" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense" xlink:label="ValuationAllowancesAndReservesChargedToCostAndExpense" xlink:title="ValuationAllowancesAndReservesChargedToCostAndExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="ValuationAllowancesAndReservesChargedToCostAndExpense" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureLineItems to ValuationAllowancesAndReservesChargedToCostAndExpense" order="3.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDeductions" xlink:label="ValuationAllowancesAndReservesDeductions" xlink:title="ValuationAllowancesAndReservesDeductions" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="ValuationAllowancesAndReservesDeductions" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureLineItems to ValuationAllowancesAndReservesDeductions" order="4.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable" xlink:label="ValuationAndQualifyingAccountsDisclosureTable" xlink:title="ValuationAndQualifyingAccountsDisclosureTable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="ValuationAndQualifyingAccountsDisclosureLineItems" xlink:to="ValuationAndQualifyingAccountsDisclosureTable" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureLineItems to ValuationAndQualifyingAccountsDisclosureTable" order="5.0" t1:closed="true" t1:contextElement="segment" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis" xlink:label="ValuationAllowancesAndReservesTypeAxis" xlink:title="ValuationAllowancesAndReservesTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="ValuationAndQualifyingAccountsDisclosureTable" xlink:to="ValuationAllowancesAndReservesTypeAxis" xlink:title="definition: ValuationAndQualifyingAccountsDisclosureTable to ValuationAllowancesAndReservesTypeAxis" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="ValuationAllowancesAndReservesDomain" xlink:title="ValuationAllowancesAndReservesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="ValuationAllowancesAndReservesTypeAxis" xlink:to="ValuationAllowancesAndReservesDomain" xlink:title="definition: ValuationAllowancesAndReservesTypeAxis to ValuationAllowancesAndReservesDomain" order="1.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain" xlink:label="ValuationAllowancesAndReservesDomain_2" xlink:title="ValuationAllowancesAndReservesDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="ValuationAllowancesAndReservesTypeAxis" xlink:to="ValuationAllowancesAndReservesDomain_2" xlink:title="definition: ValuationAllowancesAndReservesTypeAxis to ValuationAllowancesAndReservesDomain_2" order="2.0" />
    <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForCreditLossMember" xlink:label="AllowanceForCreditLossMember" xlink:title="AllowanceForCreditLossMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ValuationAllowancesAndReservesDomain" xlink:to="AllowanceForCreditLossMember" xlink:title="definition: ValuationAllowancesAndReservesDomain to AllowanceForCreditLossMember" order="1.0" />
  </link:definitionLink>
</link:linkbase>
