FF.TO · 2025-11-18 12:00:00

First Mining Announces Updated Pre-Feasibility Study for the Springpole Gold Project, Ontario, Canada Pre-Tax NPV5% of US$3.2 billion, Pre-Tax IRR of 54% After-Tax NPV5% of US$2.1 billion, After-Tax IRR of 41% Average Annual Gold Production of 330 koz and AISC of US$877/oz in Years 1 through 5

Drill Results Economic Studies

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NEWS RELEASE

First Mining Announces Updated Pre-Feasibility Study

for the Springpole Gold Project, Ontario, Canada

Pre-Tax NPV5% of US$3.2 billion, Pre-Tax IRR of 54%

After-Tax NPV5% of US$2.1 billion, After-Tax IRR of 41%

Average Annual Gold Production of 330 koz and AISC of US$877/oz in Years 1 through 5

November 18, 20 25 – Vancouver, Canada – First Mining Gold Corp. (“First Mining” or the “Company”)

(TSX: FF) (OTCQX: FFMGF) (FRANKFURT: FMG) is pleased to announce the positive results of an updated Pre-

Feasibility Study (“2025 PFS”) completed for its 100% -owned Springpole Gold Project (the “ Project” or

“Springpole”) located in Ontario, Canada. The 2025 PFS results support a 30,000 tonnes-per-day (“tpd”)

open pit mining operation.

2025 PFS Highlights12

• US$3.2 billion pre-tax net present value at a 5% discount rate ( “NPV5%”) at US$3,100/oz gold (“Au”),

increasing to US$5.6 billion at US$4,200/oz Au2

• US$2.1 billion after-tax NPV5% at US$3,100/oz Au, increasing to US$3.8 billion at US$4,200/oz Au

• 54% pre-tax internal rate of return (“IRR”) at US$3,100/oz increasing to 82% at $4,200/oz Au

• 41% after-tax IRR at US$3,100/oz Au increasing to 63% at US$4,200/oz Au

• Life of mine (“LOM”) of 9.4 years

• After-tax payback of 1.8 years and reducing to 1.2 years at US$4,200/oz Au

• Initial capital costs estimated at US$1,104 million, sustaining capital costs estimated at US$323 million,

plus US$40 million in closure costs (excluding plant closure)

• Average annual payable gold production of 330 koz per year (Years 1 to 5); 281 koz per year LOM

• Total net cash costs3 of US$742/oz (Years 1 to 5); and US$802/oz LOM

• Net All-In Sustaining Costs (“AISC”)3 of US$877/oz (Years 1 to 5), and AISC US$938/oz (LOM)

“We are pleased to announce a very positive updated PFS at our Springpole Gold Project that reinforces its

position as one of the largest and most robust undeveloped gold and silver projects in Canada”, stated Dan

Wilton, CEO of First Mining. “Since our original PFS was published in 2021, we have completed significant

engineering work, the results of which have been reflected in the updated infrastructure and design plans that

First Mining has carried through the Environmental Assessment process. At the s ame time, this study

demonstrates the strong leverage to gold price the Project possesses, and clearly demonstrates the potential

for Springpole to be one of the largest economic drivers in northwestern Ontario for a generation to come,

delivering hundreds of jobs and careers in the region, significant contracting opportunities for regional and

Indigenous businesses and more than $7 billion in gro ss domestic product , as well as generational

opportunities and potential infrastructure improvements for the Ind igenous communities in the area. First

1 Base case parameters assume a gold price of US$3,100/oz, silver price of US$35.50/oz, and an exchange rate (C$ to US$) of 0.74. All currencies are

reported in U.S. dollars unless otherwise specified. NPV calculated as of the commencement of construction and excludes all pre-construction costs.

2 US$4,200/oz Au spot case also based on US$51/oz Ag and 0.71 (C$ to US$).

3 Initial capital costs, total cash costs and all -in sustaining costs are non -IFRS measures widely used in the mining industry as a benchmark for

performance, but do not have standardized meanings under the Company's financial reporting framework. The metho ds used by the Company to

calculate such measures may differ from methods used by other companies with similar descriptions. See “Non-IFRS Financial Measures” at the end

of this news release for further details of these measures.

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Mining continues to make progress on the Federal and Provincial Environmental Assessment processes,

important consultation processes with Indigenous communities, and expect s to provide updates in the

coming months.”

This 2025 PFS for the Springpole Gold Project was prepared by Ausenco Engineering Canada ULC

(“Ausenco”) of Vancouver, Canada, and a technical report summarizing the 2025 PFS will be filed by the

Company on SEDAR+ within 45 days of this news release.

2025 PFS Overview

The Springpole Gold Project, located in Ontario, Canada, is one of the largest undeveloped gold resources in

North America. The Project is located approximately 110 kilometres northeast of Red Lake and within 18 km

of road access. The 2025 PFS provides for an updated resource model for Springpole including an Indicated

Mineral Resource of 191Mt at 0.78 g/t Au for 4.8 million ounces (“Moz”) of gold and 4.6 g/t Ag for 28 Moz of

silver. The Inferred Mineral Resource category hosts 64 Mt at 0.38 g/t Au for 0.8 Moz of gold and 3.1 g/t Ag for

6.5 Moz of silver.

The 2025 PFS evaluates recovery of gold and silver from a 30,000 tpd open pit operation, with a process plant

planned to include crushing, grinding, and flotation, with fine grinding of the flotation concentrate and

separate agitated leaching circuits for both the reground flotation concentrate and the flotation tailings,

followed by a carbon-in-pulp recovery process and a Merrill-Crowe circuit to produce doré bars. Tailings and

mine rock are proposed to be securely stored at the Project’s Co-Disposal Facility (“CDF”) designed by WSP

Canada, Inc. and reviewed by the Independent Tailings and Geotechnical Review Board established for the

Project in 2023. The leached sulphur containing (“PAG”) flotation tailings are stored in a downstream

constructed and raised CDF south cell which is lined. T he de sulphurized flotation (“NAG”) tailings are

thickened and co-disposed with mine rock in the CDF north cell.

Certain important parameters of the 2025 PFS are presented in the following table:

Table 1: Key Parameters

Key Assumptions LOM Years 1 to 5

Base Case Commodity Prices US$3,100/oz Au, US$35.50/oz Ag

Exchange Rate (C$ to US$) 0.74

Production Profile LOM Years 1 to 5

Total Tonnes Processed (Mt) 102.0 53.6

Total Tonnes Waste (Mt) 309.5 217.0

Mill Grade - Gold, Silver 0.94 g/t Au, 4.9 g/t Ag 1.09 g/t Au, 5.7 g/t Ag

Mine Life 9.4 years 5.0 years

Throughput (tpd) 30,000 30,000

Strip Ratio (waste:ore) 3.0 : 1 3.2 : 1

Overall Recovery - Gold, Silver 86.0% Au, 86.2% Ag 86.7% Au, 87.1% Ag

LOM Metal Recovered - Gold, Silver 2.6 Moz Au, 13.8 Moz Ag 1.6 Moz Au, 8.5 Moz Ag

Average Annual Recovered - Gold, Silver 281 koz Au, 1,468 koz Ag 330 koz Au, 1,704 koz Ag

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Unit Operating Costs LOM Years 1 to 5

Total Cash Cost1 US$802/oz Au

(net of by-products)

US$742/oz Au

(net of by-products)

AISC1 US$938/oz Au

(net of by-products)

US$877/oz Au

(net of by-products)

Project Economics - US$3,100/oz Au Price Pre-Tax Post-Tax

NPV5% US$3.2 billion US$2.1 billion

IRR 53.8% 40.8%

Payback Period 1.4 Years 1.8 Years

LOM Cash Flow US$4.6 billion US$3.1 billion

Economic Sensitivities

The Project economics and cash flows are highly sensitive to changes to the gold price as presented in the

following tables.

Table 2: Springpole Economic Sensitivity to Gold Price

Gold Price

(US$/oz) $2,450 $2,800 $3,100 $3,500 Spot2

($4,200)

Pre-Tax NPV5% US$2.0 billion US$2.6 billion US$3.2 billion US$4.0 billion US$5.6 billion

Pre-Tax IRR 37.8% 46.7% 53.8% 62.7% 82.1%

After-Tax NPV5% US$1.3 billion US$1.7 billion US$2.1 billion US$2.7 billion US$3.8 billion

After-Tax IRR 28.6% 35.4% 40.8% 47.7% 62.6%

Table 3: Springpole Economic Sensitivity to Initial Capital Costs

Initial Capital +20% +10% - -10% -20%

Pre-Tax NPV5% US$3.0 billion US$3.1 billion US$3.2 billion US$3.3 billion US$3.4 billion

Pre-Tax IRR 44.9% 49.0% 53.8% 59.4% 66.1%

After-Tax NPV5% US$2.0 billion US$2.1 billion US$2.1 billion US$2.2 billion US$2.3 billion

After-Tax IRR 34.0% 37.2% 40.8% 45.2% 50.4%

1 Cash costs and AISC are non -IFRS measures widely used in the mining industry as a benchmark for performance, but do not have standardized

meanings under the Company's financial reporting framework. See “Non-IFRS Financial Measures” at the end of this news release for further details

of these measures.

2 Spot price of US$4,200/oz Au, US$51/oz Ag and 0.71 (C$ to US$).

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Table 4: Springpole Economic Sensitivity to Operating Costs

Operating Costs +20% +10% - -10% -20%

Pre-Tax NPV5% US$2.9 billion US$3.0 billion US$3.2 billion US$3.4 billion US$3.6 billion

Pre-Tax IRR 49.9% 51.8% 53.8% 55.7% 57.5%

After-Tax NPV5% US$1.9 billion US$2.0 billion US$2.1 billion US$2.2 billion US$2.4 billion

After-Tax IRR 37.8% 39.3% 40.8% 42.3% 43.8%

Key Changes from 2021 Pre-Feasibility Study

Since the release of the 2021 PFS, First Mining has continued to advance Project engineering in support of

addressing the Provincial and Federal E nvironmental Assessment processes, and the consultation

processes with local and Indigenous communities. This work, which remains on-going has resulted in several

updates to the Project design since 2021. The following areas reflect the key design optimizations from the

2021 PFS to date that have been brought forward in the 2025 PFS:

• The filter plant for NAG tailings was removed from the flowsheet given the optimization to a thickened

tailings product instead of dry filtered tailings.

• The tailings and mine rock management strategy has been advanced since the 2021 PFS. A separate

flotation and leach circuit will sequester the sulphur concentrate PAG tailings. This allows the PAG

tailings to be isolated and placed saturated during operations in the CDF south cell to mitigate the

potential onset of acid generation.

• PAG mine rock will be placed in the centre of the north cell. T hickened NAG tailings, hydraulically

transported via a pipeline, will encapsulate the PAG mine rock significantly reducing oxygen ingress

to prevent oxidation of PAG mine rock improving environmental performance.

• A Merrill-Crowe circuit was added to the gold recovery circuits in order to manage ore variability and

high silver grades.

• An airstrip was added to the site layout to be co -located adjacent to the mine access road that will

facilitate up to Dash-8 size aircraft.

• A contact water management system will collect and treat site runoff and intercept potential seepage

from the CDF.

• The closure design has been advanced to include a new enhanced fish habitat development area of

46 hectares which results in a net gain in Springpole Lake surface area at closure with corresponding

benefits for fish and fish habitat.

• Two construction phase quarry sources within the Project footprint have been identified to source

clean construction material early on with one adjacent to the two dikes and the second within the

CDF footprint. This results in readily available material to initiate the construction of key Project

infrastructure early on at low cost while maintaining a small overall Project footprint.

• The tonnes processed has been reduced from the 2021 PFS as a result of an updated pit design

requiring reduced pit slope angles in the southwest portion of the open pit. Opportunities exist to

optimize the pit design as the Project advances with additional drilling programs planned in support

of a feasibility study. The reduction in the tonnes is partially offset by the 154% increase in contained

gold ounces in the Inferred Resource category which will continue to be defined with further drilling

and opportunities at Springpole Southwest and East targets . See Project Enhancement

Opportunities section.

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• Process and equipment changes are as follows:

o Flotation Tails Thickener diameter reduced to 40 m (previously 41 m)

o Flotation Concentrate Thickener diameter reduced to 23 m (previously 30 m)

o CCD Thickeners diameter reduced to 23 m (previously 30 m)

o Clarifier diameter reduced to 29 m (previously 33 m)

o Flotation Tailings Leach Tanks diameter decreased to 17.0 m (previously 19.3 m)

o Concentrate Pre-Oxidation Tank diameter decreased to 14.7 m (previously 15.2 m)

o Tails Cyanide Detox Tanks diameter increased to 11.9 m (previously 6.4 m)

o Concentrate Cyanide Detox Tanks diameter increased to 7.1 m (previously 6.4 m)

o Tailings Surge Tanks diameter decreased to 15.9 m (previously 19.6 m)

o Regrind Mills quantity reduced to two (2) (previously three (3))

o Concentrate Leach Tanks quantity reduced to four (4) and the diameter reduced to 10.5 m

(previously six (6) with a diameter of 12.3 m)

o Flotation Cells quantity reduced to five (5) and capacity increased to 300 m³ (previously six

(6) with a capacity of 200 m³)

Mineral Processing and Metallurgical Testing

The 2025 PFS reflects updated recoveries for both gold and silver that resulted from updated metallurgical

test work completed since the 2021 PFS. The test work focused on understanding the variability in gold and

silver recoveries as well as optimizing the process flowsheet.

Based on the test work carried out, a flowsheet that includes flotation followed by leaching of reground

concentrate and flotation tails presents as the most beneficial processing route for the Project. This

flowsheet is based on a primary grind size of 80% passing or P80 150 micrometres (“µm”) ahead of flotation,

with flotation concentrate being reground to approximately 17 µm ahead of agitated leaching. The overall

recoveries expected and used for the economics presented in the 2025 PFS are 86.0% for gold and 86.2% for

silver. The increase in gold / decrease in silver recoveries in the 2025 PFS stems primarily from a better

understanding of the ore variability. First Mining plans to undertake follow -up metallurgical test work to

investigate additional opportunities to further increase recoveries and believes that this remains an important

focus area for further improving the economics of the Project.

Mineral Resource and Mineral Reserve Estimates

The updated 2025 mineral resource model prepared by SRK Consulting (Canada) Inc. (“SRK”) utilizes results

from 499 core boreholes drilled by First Mining and previous property owners. The Mineral Resource Estimate

(“MRE”) at the Springpole Gold Project is shown below.

Table 5: Mineral Resource Statement Inclusive of Mineral Reserves (effective September 30, 2025)

Category Quantity Grade Metal

Au Ag Au Ag

(Mt) (g/t) (g/t) (Moz) (Moz)

Open Pit

Indicated 191 0.78 4.6 4.8 28.0

Inferred 64 0.38 3.1 0.8 6.5

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Notes:

1. Mineral resources are reported in relation to a conceptual pit shell. Mineral resources are not mineral reserves and do not have

demonstrated economic viability. All figures are rounded to reflect the relative accuracy of the estimate. All composites have been

capped where appropriate.

2. The MRE was completed under the supervision of Gilles Arseneau, P.Geo., from SRK who is a Qualified Person as defined under NI 43-

101.

3. Open pit mineral resources are reported at a cut-off grade (“COG”) of 0.20 g/t Au. COGs are based on a gold price of US$2,450/oz and a

gold processing recovery of 87.2% and a silver price of US$27.50/oz and a silver processing recovery of 85.5%.

4. Preliminary mining cost assumptions of C$2.60/tonne mined of waste, C$2.30/tonne mined of ore, and C$2.00/tonne mined of

overburden, with an incremental mining cost of C$0.02/tonne/6m mined.

5. Preliminary processing cost assumptions of C$14.50/tonne processed, general & administration assumption of C$0.90/tonne

processed, stockpile cost assumption of C$0.75/tonne processed, and incremental ore mining cost of C$0.56/tonne processed.

Overall pit shell slope angles ranged from 20 - 45°.

The resource model includes mineralized material in the Camp, East Extension and Portage zones spanning

1,860 m in the southeast direction along the axis of the Portage zone and 900 m in the northeast direction

perpendicular to the long axis of the Portage zone. Resource modelling includes mineralized material

generally ranging from 340 m to 440 m below surface.

At the reported 0.20 g/t cut-off grade, while the Indicated mineral resource in the new MRE is comparable to

the previous 2021 PFS, the new estimate reflects a 154% increase in contained gold ounces in the Inferred

Resource category. The increase in Inferred ounces is largely a result of the expansion of the Portage Zone

from additional drilling completed since 2022, including the discovery of additional gold mineralization in the

southwest pit area.

Grade Sensitivity Analysis

The Mineral Resources of the Springpole Gold Project are variable depending upon the selected COG. To

illustrate this sensitivity, the global block model quantities and grade estimates within the conceptual pit

used to constrain the Mineral Resources are p resented below at different cut -off grades for the Indicated

Mineral Resource and for the Inferred Mineral Resource.

Indicated Block Model Quantities and Grade Estimates at Cut-off Grades

Table 6: Indicated Block Model Quantities and Grade Estimates at Cut -off Grades

COG Quantity Grade Grade

Au (g/t) (Mt) Au (g/t) Ag (g/t)

0.10 218 0.70 4.2

0.20 191 0.78 4.6

0.25 176 0.83 4.8

0.30 160 0.88 5.0

0.35 145 0.94 5.2

0.40 131 1.00 5.4

0.50 107 1.12 5.9

0.60 87 1.25 6.2

0.70 70 1.39 6.6

0.80 58 1.54 6.9

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Table 7: Inferred Block Model Quantities and Grade Estimates at Cut -off Grades

COG Quantity Grade Grade

Au (g/t) (Mt) Au (g/t) Ag (g/t)

0.10 80 0.34 2.9

0.20 64 0.38 3.1

0.25 53 0.42 3.3

0.30 41 0.46 3.6

0.35 31 0.51 3.9

0.40 22 0.56 4.1

0.50 11 0.66 4.1

0.60 6 0.78 4.3

0.70 3 0.90 4.6

0.80 2 1.03 5.2

Notes:

1. The reader is cautioned that the figures in the above tables should not be misconstrued with a mineral resource statement. Th e

figures are only presented to show the sensitivity of the block model estimates to the selection of COG. Mineral Resource base case

is highlighted in grey.

Note on Inferred Resources

An Inferred Mineral Resource is that part of a mineral resource for which quantity and grade or quality are estimated on

the basis of limited geological evidence and sampling. Geological evidence is sufficient to imply but not verify geological

and grade o r quality continuity. An Inferred Mineral Resource has a lower level of confidence than that applying to an

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.

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. The quantity and grade of reported Inferred Mineral Resources in this

estimation are uncertain in nature and there has been insufficient exploration to potentially convert some or all of these

Inferred Mineral Resources as an Indicated or Measured Mineral Resources and it is uncertain if further exploration will

result in upgrading them to the Indicated or Measured Mineral Resource category. The current proportion of the resource

classified as Inferred is about 25% of total tonnes, and 14% of contained gold. The Mineral Resources in this statement

were estimated using the current CIM Definition Standards for Mineral Resources and Mineral Reserves (CIM May 2014).

The Mineral Reserves for the Springpole Gold Project are based on the conversion of Indicated Mineral

Resources within the current pit design. The Springpole Gold Project Mineral Reserves are shown below:

Table 8: Springpole Proven and Probable Reserves