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UPDATED DUPARQUET RESOURCE - SEPTEMBER 2023 PEA Duparquet deposit mineral resource estimated updated in Sept 2022 First Mining's 100% owned Pitt Gold and Duquesne deposits mineral resource estimate updated in Aug 2023 and will form part of the consolidated Duparquet Gold Project Increases Inferred Mineral Resource by more than 1 Moz Au Total M&I of 3.4 Moz Au and Inferred of 2.6 Moz Au Consolidated Duparquet Gold Project Mineral Resource Estimate G Duparquet Deposit Mineral Resource Estimate (Sept 2022) Area Cut- (Mining off Method) (g/t) Measured Resource Indicated Resource FIRST MINING Inferred Resource Tonnage Au (g/t) Ounces Tonnage (t) Au (g/t) Ounces Tonnage (t) Au (g/t) Ounces Open Pit 0.40 163,700 1.37 7,200 59,410,600 1.52 2,909,600 28,333,000 1.07 970,400 UG Mining 1.50 5,506,900 2.26 399,300 9,038,900 2.29 665,600 Tailings 0.40 19,900 2.03 1,300 4,105,200 0.93 123,200 Total 183,600 1.43 8,500 69,022,700 1.55 3,432,100 37,371,900 1.36 1,636,000 GOLD Pitt Gold & Duquesne Deposits Mineral Resource Estimate (Sept 2023) Measured Resource Indicated Resource Inferred Resource Pitt Gold Inferred Resource Duquesne Inferred Resource Area (Mining Method) Tonnage (t) Au (g/t) Ounces Tonnage (t) Au (g/t) Au Ounces Tonnage (t) Ounces Area (Mining Method) Cut-off (g/t) (g/t) Tonnage (t) Au (g/t) Ounces Tonnage (t) Au (g/t) Ounces Open Pit 163,700 1.37 7,200 59,410,600 1.52 2,909,600 34,633,000 1.16 1,286,400 Open Pit 0.50 6,300,000 1.56 316,000 UG Mining 5,506,900 2.26 399,300 16,189,000 2.60 1,354,100 UG Mining 1.75 2,120,000 2.75 187,200 5,030,000 3.10 501,400 Tailings 19,900 2.03 1,300 4,105,200 0.93 123,200 Total 2,120,000 2.75 187,200 11,330,000 2.24 817,400 Total 183,600 1.43 8,500 69,022,700 1.55 3,432,100 50,822,000 1.62 2,640,500 Note: Further details can be found in the technical report titled "NI 43-101 Technical Report: Preliminary Economic Assessment, Duparquet Project, Quebec, Canada", dated October 20, 2023, as filed on SEDAR+ and on www.firstmininggold.com TSX: FF | OTCQX: FFMGF | FRANKFURT: FMG | www.firstmininggold.com | 28

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