First Mining Files NI 43-101 Technical Report on the Updated Mineral Resource Estimate for the Duparquet Gold Project,

VANCOUVER, BC, Oct. 6, 2022 /PRNewswire/ – First Mining Gold Corp. (“First Mining” or the “Company”) (TSX: FF) (OTCQX: FFMGF) (FRANKFURT: FMG) is pleased to announce it has filed on SEDAR a Technical Report prepared in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects (“NI 43-101“) on the Duparquet Gold Project (“Duparquet” or the “Project“) titled “NI 43-101 Technical Report and Mineral Resource Estimate Update for the Duparquet Project, Quebec, Canada,” dated October 6, 2022 with an effective date of September 12, 2022.

The full Mineral Resource Estimate (“MRE“) Technical Report prepared by InnovExplo Inc. in Val-d’Or (Quebec), can be found on the Company’s website at www.firstmininggold.com and on SEDAR under the Company’s issuer profile at www.sedar.com.

The Duparquet Gold Project is a multi-million ounce advanced exploration and mining development asset located in the Abitibi region of the province of Quebec, approximately 50 km north of the city of Rouyn-Noranda. The Duparquet deposit hosts a gold Resource of 3.4 Moz in the Measured and Indicated category, and an additional 1.6 Moz Au Inferred Resource derived from the master database of drill data, which contains 904 holes totalling 270,119m and 173,831 sampled intervals.  Existing infrastructure at the Project site includes paved provincial highways from Rouyn-Noranda to the south and LaSarre to the north and direct access to Quebec’s hydroelectric power grid.  In addition, the near-by communities of Duparquet, Ruoyn-Noranda and LaSarre have strong histories of sustainable mining practices.

Table 1: Duparquet Gold Project Mineral Resource Estimate

Notes to accompany the Mineral Resource Estimate:

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1. The independent and qualified persons for the mineral resource estimate, as defined by NI 43 101, are Marina Iund, P.Geo., Carl Pelletier, P.Geo., Simon Boudreau, P.Eng. from InnovExplo Inc. and Guy Comeau, P.Eng. from Soutex. The effective date of the estimate is September 12, 2022.

2. These mineral resources are not mineral reserves, as they do not have demonstrated economic viability. There is currently insufficient data to define these Inferred mineral resources as Indicated or Measured mineral resources and it is uncertain if further exploration will result in upgrading them to an Indicated or Measured mineral resource category.  The mineral resource estimate follows current CIM Definition Standards.

3. The results are presented in situ and undiluted and have reasonable prospects of economic viability.

4. 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.

5. 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.

6. In-pit and Underground: 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. Grade interpolation was obtained by ID2 using hard boundaries. 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.

7. In-pit and Underground: A density value of 2.73 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.

8. In-pit and Underground: 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).

9. 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. It 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 to 17.0; 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.).

10. The number of metric tons and ounces was rounded to the nearest hundred, following the recommendations in NI 43 101. Any discrepancies in the totals are due to rounding effects.

11. The authors are not aware of any known environmental, permitting, legal, title-related, taxation, socio-political, or marketing issues, or any other relevant issue not reported in the Technical Report, that could materially affect the Mineral Resource Estimate.

Table 2: Cut-off grade sensitivity for the in-pit and underground portions of the Duparquet Gold Project

InnovExplo Inc., the authors of the Technical Report, concluded that:

• The database supporting the 2022 MRE is complete, valid and up to date.

• Geological and gold-grade continuity has been demonstrated for all 72 mineralized zones.

• The key parameters of the 2022 MRE (density, capping, compositing, interpolation, search ellipsoid, etc.) are supported by data and statistical and/or geostatistical analysis.

• The 2022 MRE includes measured, indicated and inferred resources for a combination of two mining scenarios: open pit and selective underground. The 2022 MRE complies with CIM Definition Standards and CIM Guidelines.

• Two cut-off grades of 0.40 and 1.50 g/t Au were used, corresponding to potential open pit and selective underground mining scenarios.

• Cut-off grades were calculated at a gold price of US$1,650 per troy ounce and an exchange rate of 1.31 USD/CAD, using reasonable mining, processing and G&A costs.

• In a combined pit and selective underground mining scenario, the Project contains an estimated M+I Resource of 65,081,200 t at 1.58 g/t Au for 3,316,100 oz of gold and an Inferred Resource of 37,371,900 t at 1.36 g/t Au for 1,636,000 oz of gold. The Project also contains the Beattie mine tailings with an estimated M+I Resource of 4,125,100 t at 0.94 g/t Au for 124,500 oz of gold.

• The results of the 2022 MRE represent a 10.5% increase in the M+I Resource and a 13.4% increase in the Inferred Resource compared to the previous 2014 MRE of Poirier et al., 2014. The increase in the M+I Resource is due to a deeper optimized shell and the updated economic parameters. The same reasons combined with the addition of 55 drill holes explain the increase in Inferred resources.

• Based on metallurgical tests, the Duparquet project appears amenable to standard gold recovery processes. A combination of flotation, pressure oxidation and cyanide leach processes has shown a gold recovery ranging from 94.7% to 96.5%.

• Additional diamond drilling on multiple zones would likely upgrade some of the Inferred Resource to the Indicated category and/or add to the Inferred Resource since most of the mineralized zones have not been fully explored at depth or close to…