First Mining Mineral Resources

* General Notes for Above Resources:

a) The rounding of tonnes may result in apparent differences between tonnes, grade and contained ounces.

b) Mineral resources that are not mineral reserves do not have demonstrated economic viability. The estimate of mineral resources may be materially affected by environmental permitting, legal, title, taxation, sociopolitical, marketing or other relevant issues.

c) The PEA is preliminary in nature, that it includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the PEA will be realized.

(1) Notes for Cameron:

• Based on the technical report titled “Technical Report on the Cameron Gold Deposit, Ontario, Canada”, dated effective January 17, 2017, which was prepared for First Mining by Optiro Pty Limited in accordance with NI 43-101, and which is available under First Mining's SEDAR profile at www.sedar.com.
• 2014 CIM Definition Standards were followed for classification of mineral resources.
• The mineral resource estimate is classified as Measured, Indicated and Inferred mineral resources.
• The mineral resource has been estimated using a gold price of US$1,350 per ounce.
• The mineral resource was estimated using a block model. Three dimensional wireframes were generated using geological information. The ordinary kriging estimation method was used to interpolate grades into blocks. Blocks were sub-blocked to more accurately reflect the volume of the wireframes.
• Mineral resources which are not mineral reserves do not have demonstrated economic viability. An Inferred Mineral Resource has a lower level of confidence than that applying to a Measured and Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of Inferred Mineral Resources could be upgraded to Indicated Mineral Resources with continued exploration.
• Numbers may not add due to rounding.
• The mineral resource for the Cameron Gold Project does not include the mineralized material from the Dubenski and Dogpaw areas.

(2) Notes for Duparquet:

• The independent qualified persons for the Duparquet mineral resource estimate, as defined by NI 43-101, are Marina Iund, P.Geo., Carl Pelletier, P.Geo. and Simon Boudreau, P.Eng. from InnovExplo. The effective date of the estimate is September 12, 2022.  
• The independent qualified persons for the Pitt Gold and Duquesne mineral resource estimates, as defined by NI 43 101, are Olivier Vadnais-Leblanc, P.Geo., Carl Pelletier, P.Geo., and Simon Boudreau, P.Eng. from InnovExplo. The effective date of the estimate is August 31, 2023.
• Mineral resources which are not mineral reserves do not have demonstrated economic viability. An Inferred Mineral Resource has a lower level of confidence than that applying to a Measured and Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of Inferred Mineral Resources could be upgraded to Indicated Mineral Resources with continued exploration.
• The results are presented in situ and undiluted and have reasonable prospects of eventual economical extraction.
• In-pit and Underground estimates encompass sixty (60) mineralized domains and one dilution envelop using the grade of the adjacent material when assayed or a value of zero when not assayed; The tailings estimate encompass four (4) zones.
• Duparquet: In-pit and Underground: High-grade capping of 25 g/t Au; Tailings: High-grade capping of 13.0 g/t Au for Zone 1, 3.5 g/t Au for Zone 2, 1.7 g/t Au for Zone 3 and 2.2 g/t Au for Zone 4. High-grade capping supported by statistical analysis was done on raw assay data before compositing.
• Pitt Gold: Underground: High-grade capping of 20 g/t Au. High-grade capping supported by statistical analysis was done on composited assays.
• Duquesne: In-pit and Underground: High-grade capping of 55 g/t Au. High-grade capping supported by statistical analysis was done on composited assays.
• In-pit and Underground: For Duparquet, the estimate used a sub-block model in GEOVIA SURPAC 2021 with a unit block size of 5m x 5m x 5m and a minimum block size of 1.25m x 1.25m x1.25m.  For Pitt Gold and Duquesne, the estimates used a sub-block model in GEOVIA SURPAC 2023 with a unit block size of 6m x 6m x 6m and a minimum block size of 1.5m x 0.5m x0.5m.  Grade interpolations were obtained by ID2 using hard boundaries. Duparquet Tailings: The estimate used a block model in GEOVIA GEMS with a block size of 5m x 5m x 1m. Grade interpolation was obtained by ID2 using hard boundaries.
• In-pit and Underground: For Duparquet, a density value of 2.73 g/cm3 was used for the mineralized domains and the envelope. For Pitt Gold and Duquesne, a density value of 2.7 g/cm3 was used for the mineralized domains and the envelope.  A density value of 2.00 g/cm3 was used for the overburden. A density value of 1.00 g/cm3 was used for the excavation solids (drifts and stopes) assumed to be filled with water. Tailings: A fixed density of 1.45 g/cm3 was used in zones and waste.  
• In-pit and Underground: For Duparquet, the mineral resource estimate is classified as Measured, Indicated and Inferred. The measured category is defined by blocks having a volume of at least 25% within an envelope built at a distance of 10 m around existing channel samples. The Indicated category is defined by blocks meeting at least one (1) of the following conditions: Blocks falling within a 15-m buffer surrounding existing stopes and/or blocks for which the average distance to composites is less than 45 m. A clipping polygon was generated to constrain Indicated resources for each of the sixty (60) mineralized domains. Only the blocks for which reasonable geological and grade continuity have been demonstrated were selected. All remaining interpolated blocks were classified as Inferred resources. Blocks interpolated in the envelope were all classified as Inferred resources. Tailings: The Measured and Indicated categories were defined based on the drill hole spacing (Measured: Zones 1 and 2 = 30m x 30m grid; Indicated: Zone 3 = 100m x 100m grid and Zone 4 = 200m x 200m grid).  For Pitt Gold and Duquesne, the mineral resource estimate are completely classified as Inferred due to a lack of confidence in certain drill hole collar and underground development locations.
• The Mineral Resource Estimate for Duquesne and Pitt Gold was prepared using 3D block modelling and the inverse distance squared (“ID2”) interpolation method.
• The mineral resources are categorized as Inferred based on drill spacing, as well as geological and grade continuity. A maximum distance to the closest composite of 75 m for Inferred in all zones for Duquesne of 210 m for Inferred in all zones for Pitt Gold.
• The reasonable prospect for an eventual economical extraction is met by having used reasonable cut-off grades both for a potential open pit and underground extraction scenarios (minimum mining width of 2m) and constraining volumes (Deswik optimized shapes and Whittle optimized pit-shells).  
• In-pit and Underground: The mineral resource estimate is locally pit-constrained with a bedrock slope angle of 50° and an overburden slope angle of 30°. The out-pit mineral resource met the reasonable prospect for eventual economic extraction by having constraining volumes applied to any blocks (potential underground extraction scenario) using DSO. Duparquet resources is reported at a rounded cut-off grade of 0.4 g/t Au (in-pit and tailings) and 1.5 g/t Au (UG). The cut-off grades were calculated using the following parameters: mining cost = CA$70.00 (UG); processing cost = CA$11.9 (tailing) to CA$17.0 (pit& UG); G&A = CA$8.75; refining and selling costs = CA$ 5.00; gold price = US$ 1,650/oz; USD:CAD exchange rate = 1.31; and mill recovery = 93.9%. The cut-off grades should be re-evaluated in light of future prevailing market conditions (metal prices, exchange rates, mining costs etc.).  Duquesne resources are reported at a rounded cut-off grade of 0.5 g/t Au (in-pit) and Pitt Gold and Duquesne resources are reported at a rounded cut-off grade of 1.75 g/t Au (UG). The cut-off grades were calculated using the following parameters: mining cost = CA$84.86 (UG); processing cost = CA$21.010; G&A = CA$11.75; refining and selling costs = CA$ 5.00; gold price = US$ 1,800/oz; USD:CAD exchange rate = 1.3; and mill recovery = 90%. The cut-off grades should be re-evaluated in light of future prevailing market conditions (metal prices, exchange rates, mining costs etc.).
• The number of metric tons was rounded to the nearest thousand and ounces were rounded to the nearest hundred, following the recommendations in NI 43 101. Any discrepancies in the totals are due to rounding effects.
• The qualified persons are not aware of any known environmental, permitting, legal, title-related, taxation, socio-political, or marketing issues, or any other relevant issue not reported herein, that could materially affect the Mineral Resource Estimate.
• The PEA is preliminary in nature, that it includes inferred mineral resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the PEA will be realized.

(3) Notes for Springpole:

• Based on the technical report for the Springpole PFS entitled “NI 43-101 Technical Report and Pre-Feasibility Study on the Springpole Gold Project, Ontario Canada” which has an effective date of January 20, 2021 and is available under First Mining’s SEDAR profile at www.sedar.com.
• 2014 CIM Definition Standards were followed for the classification of mineral resources. 
• Mineral Resources potentially amenable to open pit mining are reported within an optimized constraining shell using the following parameters:
  • Metal prices of US$1,550/oz gold, US$20/oz silver, exchange rate of US$0.77:C$1
  • Mining cost of C$1.62/t, processing cost of C$15.38/t milled, G&A cost of C$1.00/t milled
  • Pit slopes varying between 35–50º depending on domain
  • Gold recovery of 88% and silver recovery of 93%
• Mineral Resources are reported at a cut-off grade of 0.3 g/t Au.

(4) Notes for Hope Brook:

• First Mining owns 20% of the Hope Brook Gold Project, and 80% is owned by Big Ridge Gold Corp. The mineral resources for Hope Brook shown in the above table reflect only the First Mining ownership interest.
• Further details on the 2023 updated mineral resource estimate on the Hope Brook Gold Project can be found in the technical report titled “Mineral Resource Estimate Update for the Hope Brook Gold Project, Newfoundland and Labrador, Canada”, prepared for Big Ridge Gold Corp. by SGS Geological Services Ltd, and dated April 6, 2023, which is available under Big Ridge’s SEDAR profile at  www.sedar.com.
• The classification of the current Mineral Resource Estimate into Indicated and Inferred is consistent with current 2014 CIM Definition Standards - For Mineral Resources and Mineral Reserves
• All figures are rounded to reflect the relative accuracy of the estimate.
• All Resources are presented undiluted and in situ, constrained by continuous 3D wireframe models, and are considered to have reasonable prospects for eventual economic extraction.
• Mineral resources which are not mineral reserves do not have demonstrated economic viability. An Inferred Mineral Resource has a lower level of confidence than that applying to a Measured and Indicated Mineral Resource and must not be converted to a Mineral Reserve. It is reasonably expected that the majority of Inferred Mineral Resources could be upgraded to Indicated Mineral Resources with continued exploration.
• The update MRE is based on data for 763 surface and underground drill holes representing 164,865 m of drilling, including data for 60 surface drill holes for 19,090 m completed by Big Ridge in 2021 and 2022.
• The mineral resource estimate is based on 2 three-dimensional ("3D") resource models for the Main Zone and 240 Zones.
• High grade capping was applied to the 1.5 m composite data. A capping value of 50 g/t Au was to the Main Zone and 40 g/t Au for the 240 Zone.
• Average density values were assigned per zone.
• Gold is estimated for each mineralization domain. Blocks (5x5x5) within each mineralized domain were interpolated using 1.5 metre capped composites assigned to that domain. To generate grade within the blocks, the inverse distance squared (ID²) interpolation method was used for all domains.
• It is envisioned that parts of the Main Zone may be mined using open pit mining methods. Open pit mineral resources are reported at a base case cut-off grade of 0.4 g/t Au within a conceptual pit shell.
• It is envisioned that parts of the Main Zone as well as the 240 Zone may be mined using underground mining methods. A selected base case cut-off grade of 2.0 g/t Au is used to determine the underground mineral resource for the Main Zone and 240 Zone.The underground Mineral Resource grade blocks were quantified above the base case cut-off grade, below the constraining pit shell and within the constraining mineralized wireframes.
• Base case cut-off grades consider a metal price of US$1750.00/oz Au and considers a metal recovery of 86 % for Au.
• The pit optimization and in-pit base case cut-off grade of 0.4 g/t Au considers a mining cost of US$2.65/t rock and processing, treatment and refining, transportation and G&A cost of US$15.60/t mineralized material, and an overall pit slope of 55°. The underground base case cut-off grade of 2.0 g/t Au considers a mining cost of US$54.00/t rock and processing, treatment and refining, transportation and G&A cost of US$15.550. The cut-off grades should be re-evaluated in light of future prevailing market conditions (metal prices, exchange rates, mining costs etc.).
• The results from the pit optimization are used solely for the purpose of testing the "reasonable prospects for economic extraction" by an open pit and do not represent an attempt to estimate mineral reserves. There are no mineral reserves on the Property. The results are used as a guide to assist in the preparation of a Mineral Resource statement and to select an appropriate resource reporting cut-off grade.
• The estimate of Mineral Resources may be materially affected by environmental, permitting, legal, title, taxation, socio-political, marketing, or other relevant issues. There is no certainty that all or any part of the Inferred Mineral Resource will be upgraded to an Indicated or Measured Mineral Resource as a result of continued exploration. There is no other relevant data or information available that is necessary to make the technical report understandable and not misleading.
• The Author is not aware of any known mining, processing, metallurgical, environmental, infrastructure, economic, permitting, legal, title, taxation, socio-political, or marketing issues, or any other relevant factors not reported in this technical report, that could materially affect the updated MRE.

(5) Notes for Pickle Crow (30%)

• First Mining owns 30% of the Pickle Crow Gold Project, and 70% is owned by FireFly Metals Ltd. The Inferred mineral resources for Pickle Crow shown in the above table reflects only the First Mining ownership interest.
• Based on the technical report titled “An Updated Mineral Resource Estimate for the Pickle Crow Property, Patricia Mining Division, Northwestern Ontario, Canada” dated June 15, 2018, which was prepared for First Mining by Micon International Limited in accordance with NI 43-101, and which is available under First Mining's SEDAR profile at www.sedar.com.
• 2014 CIM Definition Standards were followed for the classification of mineral resources.
• Diluted to a minimum 1.0 metre width.
• Entirely classified as an Inferred mineral resource.
• The narrow-vein, selective underground component of the mineral resource has been estimated at a cut-off grade of 2.6g/t Au.
• The long-hole bulk underground (moderate-grade) component of the mineral resource has been estimated at a cut-off grade of 2.0 g/t Au.
• The open pit (low-grade) component of the mineral resource has been estimated at a pit discard cut-off grade of approximately 0.5 g/t Au, using a preliminary Whittle pit shell to constrain the resource estimate and other assumed pit parameters.
• The mineral resource has been estimated using a gold price of US$1,300 per ounce.