XML 142 R115.htm IDEA: XBRL DOCUMENT
v3.25.1

MANAGEMENT OF FINANCIAL RISK (Disclosure of Nature and Extent Arising from Financial Instruments - Commodity Price Risk) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 | Dec. 31, 2023
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Increase (decrease) in sales due to price changes of commodity | $ 3,100 | $ (700)
Silver Commodity Type [member] |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Effect on Sales | $ 468 |
Change percentage, commodity | 10.00% |
Gold Commodity Type [member] |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Effect on Sales | $ 294 |
Change percentage, commodity | 10.00% |
Lead Commodity [member] |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Effect on Sales | $ 487 |
Change percentage, commodity | 10.00% |
Zinc Commodity [member] |  |
Disclosure of nature and extent of risks arising from financial instruments [line items] |  |
Effect on Sales | $ 671 |
Change percentage, commodity | 10.00% |

X
- Definition Increase (decrease) in sales due to price changes of commodity. + References No definition available. + Details
Name: | fsm_IncreaseDecreaseInSalesDueToPriceChangesOfCommodity
Namespace Prefix: | fsm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage change on commodity price percentage. + References No definition available. + Details
Name: | fsm_PercentageChangeOnCommodityPricePercentage
Namespace Prefix: | fsm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage price change on commodity effect on sales amount. + References No definition available. + Details
Name: | fsm_PercentagePriceChangeEffectOnSalesAmount
Namespace Prefix: | fsm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table. + References No definition available. + Details
Name: | ifrs-full_DisclosureOfNatureAndExtentOfRisksArisingFromFinancialInstrumentsLineItems
Namespace Prefix: | ifrs-full_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | fsm_TypeOfCommodityAxis=fsm_SilverCommodityTypeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsm_TypeOfCommodityAxis=fsm_GoldCommodityTypeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsm_TypeOfCommodityAxis=fsm_LeadCommodityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | fsm_TypeOfCommodityAxis=fsm_ZincCommodityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |