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        <link:definition>090300 - Disclosure - Revenue from Contracts with Customers (Details)</link:definition>
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  <xs:element name="FairValueAssetsLevel3TransfersOutAmount" id="mtx_FairValueAssetsLevel3TransfersOutAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" />
  <xs:element name="OtherAssetsAndDeferredChargesMember" id="mtx_OtherAssetsAndDeferredChargesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="MaximumPercentageOfTotalBenefitObligationForInternationalPensionPlans" id="mtx_MaximumPercentageOfTotalBenefitObligationForInternationalPensionPlans" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="instant" />
  <xs:element name="EmployeeVestingPeriodForDefinedBenefitPlans" id="mtx_EmployeeVestingPeriodForDefinedBenefitPlans" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="DefinedBenefitPlanOther" id="mtx_DefinedBenefitPlanOther" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" />
  <xs:element name="AverageRateOfReturnOnAssets" id="mtx_AverageRateOfReturnOnAssets" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="RealEstateAndOtherMember" id="mtx_RealEstateAndOtherMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="ActualReturnLossOnPensionAssets" id="mtx_ActualReturnLossOnPensionAssets" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="FurnitureAndFixturesAndOtherMember" id="mtx_FurnitureAndFixturesAndOtherMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="DepreciationAndDepletionExpense" id="mtx_DepreciationAndDepletionExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" />
  <xs:element name="MineralRightsAndReservesMember" id="mtx_MineralRightsAndReservesMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="WeightedAverageRemainingLeaseTermAndDiscountRatesAbstract" id="mtx_WeightedAverageRemainingLeaseTermAndDiscountRatesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="RentExpenseAbstract" id="mtx_RentExpenseAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="LesseeOperatingLeaseRemainingLeaseTerm" id="mtx_LesseeOperatingLeaseRemainingLeaseTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="SupplementalCashFlowInformationAndNonCashActivityRelatedToOurOperatingLeasesAbstract" id="mtx_SupplementalCashFlowInformationAndNonCashActivityRelatedToOurOperatingLeasesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="OperatingCashFlowsInformationAbstract" id="mtx_OperatingCashFlowsInformationAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="NonCashActivityAbstract" id="mtx_NonCashActivityAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" abstract="true" xbrli:periodType="duration" />
  <xs:element name="LesseeOperatingLeaseAssetsAndLiabilitiesBalanceSheetInformationTableTextBlock" id="mtx_LesseeOperatingLeaseAssetsAndLiabilitiesBalanceSheetInformationTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="LesseeOperatingLeaseSupplementalCashFlowInformationAndNonCashActivityTableTextBlock" id="mtx_LesseeOperatingLeaseSupplementalCashFlowInformationAndNonCashActivityTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
  <xs:element name="WeightedAverageRemainingLeaseTermAndDiscountRatesTableTextBlock" id="mtx_WeightedAverageRemainingLeaseTermAndDiscountRatesTableTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" abstract="false" xbrli:periodType="duration" />
</xs:schema>
