Mr. Dan Wilton reports

FIRST MINING ANNOUNCES POSITIVE PRELIMINARY ECONOMIC ASSESSMENT FOR THE DUPARQUET GOLD PROJECT, QUEBEC, CANADA

First Mining Gold Corp. has released the positive results of a preliminary economic assessment (PEA) completed for its 100-per-cent-owned Duparquet gold project located in the Abitibi region of Quebec, Canada. The PEA results support a 15,000-tonne-per-day open-pit and underground mining operation over an 11-year mine life. The PEA only considers the Duparquet gold deposit located on the Beattie, Donchester, Central Duparquet and Dumico claim blocks and does not include the Pitt Gold and Duquesne deposits (see mineral resource estimate section).

PEA highlights:

• $1.07-billion pretax net present value (5 per cent) and $588-million after-tax NPV (5 per cent) at $1,800 (U.S.)/ounce gold;
• 24.9-per-cent pretax IRR; 18-per-cent after-tax IRR at $1,800 (U.S.)/oz Au;
• Annual life-of-mine (LOM) recovered gold production of 233,000 oz;
• Total LOM recovered gold of 2.5 million oz (Moz) over an 11-year mine life;
• Pretax payback of 3.8 years; after-tax payback of 4.8 years;
• Initial capital costs estimated at $706-million; sustaining and underground development capital costs estimated at $738-million;
• Average annual LOM total cash cost of $751 (U.S.)/oz; average annual LOM all-in sustaining costs (AISC) of $976 (U.S.)/oz.

"This PEA demonstrates the robust economic potential of the Duparquet gold project," stated Dan Wilton, chief executive officer of First Mining. "The 200,000-plus oz per year production profile, attractive capital and operating cost profile, and strategic location of the deposit in the heart of the Abitibi gold belt all contribute to the recognition of Duparquet as one of the most meaningful development projects in Canada. We are also pleased to have completed such a robust PEA within a year of consolidating the ownership of the project. Importantly, the Duparquet gold project represents a unique opportunity to address the environmental legacy issues from the historic mining operations while delivering an important economic development opportunity for the local and indigenous communities around the project. We look forward to continuing to work with regulators, the municipality of Duparquet, and other local and indigenous communities to advance this parallel track of environmental stewardship and economic development."

This PEA for the Duparquet gold project was prepared by G Mining Services Inc. of Montreal, Que., in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects, and a technical report for the PEA will be filed by the company on SEDAR+ within 45 days of this news release.

PEA overview

The Duparquet gold project, located in the Abitibi region of Quebec, Canada, is one of the largest undeveloped gold projects in North America. The project is located immediately north of the town of Duparquet which is approximately 50 kilometres northwest of Rouyn-Noranda, Que., a major mining service centre and home to the only remaining copper smelter in Canada. Duparquet currently hosts 3.4 million ounces of gold in the indicated mineral resource category and 2.7 million ounces of gold in the inferred mineral resource category.

The PEA evaluates recovery of gold from a 15,000-tonne-per-day (tpd) open-pit and underground mining operation, with a process plant that includes crushing, grinding and flotation, producing a concentrate for sale.

Economic sensitivities

The project economics and cash flows are highly sensitive to changes in the price of gold.

Mineral resource estimate

In September, 2022, the Duparquet gold project mineral resource estimate (MRE) was updated by InnovExplo Inc. in accordance with NI 43-101 (see news release of Sept. 12, 2022, for more details). The Duparquet gold project contains 3.44 million ounces of gold in the measured and indicated category, grading 1.55 grams per tonne Au, and an additional 1.6 million ounces of gold in the inferred category, grading 1.36 g/t Au.

In August, 2023, new updated mineral resource estimates were completed on First Mining's 100-per-cent-owned Pitt Gold and Duquesne projects and have added 1.05 million ounces of gold grading 2.32 g/t Au in the inferred category, which will now form part of the larger consolidated Duparquet gold project.

Following the updated mineral resource estimate at Pitt Gold and Duquesne, the consolidated Duparquet project now contains 3.44 million ounces of gold in the measured and indicated category, grading 1.55 g/t Au, and an additional 2.68 million ounces of gold in the inferred category, grading 1.68 g/t Au.

The database used for the Duparquet MRE contains 904 holes totalling 270,119 metres and 173,831 sampled intervals. The resource area has an east-west strike length of 4.5 kilometres, a width of approximately one km and a vertical extent of 1,050 m below surface. A total of 60 mineralized zones wireframes have been created for the Duparquet deposit.

The database used for the Duquesne MRE contains 1,011 underground drill holes for a total of 51,957.43 m and 393 surface diamond drill holes (DDH) totalling 103,888.19 m. The DDH intervals used for the interpretation contain 66,411 assays taken from the 1,404 drill holes and surface channels (71,034.71 m of core). A total of 389 mineralized zones wireframes have been created for the Duquesne deposit. Mineralized zones average thickness in the deposit varies between 0.69 m and 4.28 m with an interpreted average thickness of 1.89 m.

The database used for the Pitt Gold MRE contains 163 surface diamond drill holes totalling 70,364.67 m. A total of 119 mineralized zones wireframes have been created for the Pitt Gold deposit. Mineralized zones average thickness in the deposit varies between 0.71 m and 3.03 m with an interpreted average thickness of 1.56 m.

Capital costs

The capital cost estimate for the proposed open-pit operation in the PEA is based on the scheduled plant throughput rates, as well as a review of similar-sized open-pit gold operations.

Mining capital costs

The open-pit mining activities for the project were assumed to be undertaken by an equipment financed fleet. Mining capital costs were estimated based on a detailed equipment schedule matched to the mining production schedule. Total initial mining capital was estimated at $102-million, inclusive of capitalized stripping and equipment. The capital expenditure for the underground, which starts at year 1 of open-pit operations, is $404-million of which $255-million is attributed to mine development.

Processing capital costs

The process plant was designed using conventional processing unit operations. It will nominally treat 15,000 tpd or 679 dry tonnes/hour based on 92-per-cent availability. The primary crushing plant design is based on 75-per-cent availability. The plant will operate two shifts per day, 365 days per year, and will produce a high-grade gold concentrate for sale to smelters.

Initial capital costs for the processing facility were estimated to be $190-million, excluding contingency. No major plant rebuild or expansion was considered during the LOM, with sustaining capital set to maintain the equipment in operating condition.

Operating costs

Mining costs

The PEA contemplates open-pit and underground mining undertaken by an equipment financed fleet. An average unit mining cost of $3.16 per tonne of material mined from the open pit was used in the economics. The cost estimate was built from first principles with detailed haulage profiles, and is based on experience of similar-sized open-pit operations and local conditions. The open-pit mining costs consider variations in haulage profiles by month and by year and variable equipment requirements necessary to meet the plant production.

Underground mining cost was also estimated using first principles with supplier's quotations for equipment, consumables and contractor work, and is based on experience with underground operations with similar size and environment. The underground mining costs of $44.26 per tonne of mineralized material mined from underground includes $2,257 per metre of operating expenditure development. A sustaining development cost of $16.64 per tonne is required to maintain production which is excluded from the operation costs.

Processing costs

An average cost of $10.59 per tonne of processed material was used in the PEA, based on the selected process flowsheet. This includes tailings handling, labour, consumables, maintenance and supplies. A power cost of 5.24 cents/kilowatt-hour was assumed.

Mining

Open-pit mining would occur in year 1 concurrent with underground development. Over the LOM, the open pit will deliver an average of 10,400 tpd of mineralized material to the mill. The annual peak of mineralized material delivered to the mill is 12,670 tpd in year 8. Underground production is expected to begin in year 2 with an average underground production rate of 3,500 tpd. Over an 11-year mine life, A total of 59.7 Mt of mineralized material (including preproduction) will be mined, which includes 4.1 Mt of historical tailings. The current LOM plan focuses on achieving consistent processing feed production rates, mining of higher-grade material early in the schedule, and balancing grade and strip ratios.

Mining methods

The Duparquet project is planned as a mix of conventional open-pit mine and a longhole (transversal -- longitudinal -- uppers) underground mine.

Open-pit mining will be done with the use of diesel equipment including drilling rigs and haul trucks coupled with hydraulic shovels. The project consists of seven pits with pit 1 having three phases. The LOM will last for 11 years including a preproduction and construction period where waste will be mined for construction purposes (dams, roads etc.) and mineralized material will be stockpiled ahead of the process plant commissioning.

Production drilling and mining operations will take place on a 10 m bench height. The primary production equipment includes 12-cubic-metre diesel-hydraulic shovel coupled with 65-tonne Drammis trucks for the mineralized material and 22-cubic-metre diesel-hydraulic production shovels coupled with 200-tonne off-highway mining trucks for the waste. An owner mining operation is planned with overburden stripping, topographic drilling activities, and supply of explosives outsourced to contractors.

For the underground mine, longhole stopping, both transverse and longitudinal with cemented rockfill (CRF), is the preferred mining method. Mineralized material will be removed from the stopes using a high-production-sized load-haul-dump (LHD). The underground mine's main declines will be accessible from surface through a single portal located north of the site.

In addition to the open-pit and underground mines, a portion of the historical tailings will be transported and processed at the mill. A maximum of 750,000 t of material will be processed yearly.

Metallurgical testing

The PEA reflects gold recoveries that were a result of the extensive metallurgical test work completed by Clifton Star Resources Inc. during 2012 to 2014. The test work involved several rounds of bench-scale and pilot plant testing of flotation concentration. In addition, Clifton Star completed extensive metallurgical test work on follow-on processing to treat the sulphide concentrates with fine grinding and alkaline leaching, bio-oxidation, and pressure oxidation but was not included in the PEA flowsheet.

Based on the test work carried out and trade-off studies conducted as part of the PEA, the project was scoped with a flowsheet that includes comminution circuit and rougher and cleaner flotation to produce a high-grade gold concentrate for sale. This flowsheet is based on a primary grind size of 80 per cent passing (P80) of 150 microns ahead of flotation. The gold recoveries to the flotation concentrate expected and used for the economics presented in the PEA are 89.5 per cent to a concentrate grading approximately 36 g/t Au. 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.

Processing

The preliminary process plant design for the Duparquet project is based on a robust metallurgical flowsheet to treat gold-bearing material to produce gold concentrate. The flowsheet is based on previous metallurgical test work by Clifton Star, industry standards and conventional unit operations.

The process plant is designed to nominally treat 15,000 tpd of mineralized material and reprocessing of existing tailings. The flowsheet will consist of primary crushing, SAG (semi-autogenous) and ball mill grinding, rougher and cleaner gold flotation circuits, concentrate dewatering, and loadout facilities. Flotation tailings will be dewatered in a thickener to produce a tailings slurry for storage on site. The process plant will include reagents, air systems and utilities to support the operation.

Site infrastructure

The project is located immediately north of the town of Duparquet with much of the site infrastructure optimized to utilize existing infrastructure within the town of Duparquet. No camp is planned on site and the administrative offices, the light-vehicle truck shop and warehouse, among others, are considered off site. The operation buildings, which will include the security office, offices for technical personnel, the conference rooms, a change room, an infirmary and a lunchroom, will be located at site entrance. An on-site temporary workshop is included in the initial capital with the permanent truck shop planned in year 4. The assay lab, the fuel storage (200,000 litres) and the explosive magazine, among other essential infrastructure, are also considered on site.

The infrastructure and process plant platform will be located on the north side of the pits. The waste rock stockpiles will be located on each side of the pits. A haul road is planned to connect the pits to the waste stockpiles, overburden stockpiles, process plant and tailings storage facility.

Tailings storage facility

The tailings storage facility (TSF) design will take advantage of the existing topographic and ground conditions in the eastern part of the project site. The TSF will provide enough capacity for 34.5 million cubic metres of tailings. A tailings deposit basin will be created by building a main dam at the downstream end of the valley and the tailings dams will be constructed in phases to minimize the initial capital. The process plant tailings will be pumped to the TSF through a four km pipeline and will be thickened prior to deposition. The reclaim water system will consist of a reclaim barge equipped with two reclaim water pumps.

Power infrastructure

Approximately 22.7 megawatts of electrical demand will be supplied via a new 120-kilovolt overhead transmission line, built to connect to the provincial grid's 120 kV line approximately 15 km to the southeast in Reneault Hydro-Quebec substation. Main distribution network is made at 13.8 kV from the main substation where two fully redundant power transformers are installed. Distribution to the equipment is made at 4.16 kV and 600 volts.

Environment and community

The PEA has considered and incorporated the opportunity to leverage the Duparquet gold project development with the reclamation of the brownfield site conditions including the removal and reprocessing of over 4.1 Mt of uncontained historical mine tailings. With such measures incorporated into the PEA mine plan, in combination with the ability of the project to collect and treat historically impacted groundwater via the excavation and dewatering of the open pit, the project is positioned to deliver both environmental benefits and socio-economic benefits via employment, contracting and revenue for the municipality of Duparquet. The PEA is anticipated to be refined and optimized based on consultation and input to be received by government, the municipality of Duparquet, other local and regional stakeholders, and the local first nation community.

Since acquiring the Duparquet gold project in September of 2022, First Mining has prioritized meeting the people, communities and government representatives on project planning in an open and transparent manner. First Mining published the Mines d'Or Duparquet website to share project information and has recently finished renovations required to open a First Mining community relations office in Duparquet. The project provides an opportunity to address historical environmental aspects at the project site to improve long-term sustainability and economic activity and support sustainable municipal planning and development.

The municipality of Duparquet is in the Abitibi-Temiscamingue region which has been shaped primarily by natural resource-based industries, including mining and forestry, where the mining industry accounts for one in seven jobs in the region.

Project enhancement opportunities

The PEA identified several opportunities to enhance the economics of the Duparquet gold project and will be investigated as First Mining continues to advance the project. These opportunities include:

• Exploration drilling -- opportunity to expand the resource with drilling regionally along 19 km of First Mining's property over the Destor-Porcupine fault zone; First Mining is in the process of completing an initial 5,000-metre drill program at the project and intends to start a phase II drill program later in 2023;
• Infill drilling -- opportunity to expand the resource and increase the grade profile at the project;
• Silver mineralization -- opportunity to incorporate silver mineralization into the economics; the PEA does not contemplate any payable silver ounces;
• Additional technical studies -- opportunity to optimize project economics by reducing sustaining capital, development capital and operating costs;
• Incorporating new mineral resource -- opportunity to improve project economics by incorporating new mineral resource estimates into the mine plan from nearby Pitt and Duquesne deposits, which form part of the larger Duparquet gold project;
• Regional consolidation -- opportunity to consolidate refractory deposits in the region to create a central processing facility to treat feed from other regional mines;
• Test work on historical tailings -- opportunity to optimize the blending of the old tailings through the process with additional test work;
• Metallurgical test work -- opportunity to improve metallurgical recoveries and concentrate grade with additional metallurgical test work;
• Water management -- opportunity to optimize water treatment and services estimate with additional studies;
• Tailings -- opportunity to optimize tailings and design and cost estimates with additional studies;
• Infrastructure -- opportunity to optimize town infrastructure in project design.

Qualified persons and National Instrument 43-101 technical report

The PEA for the Duparquet gold project summarized in this news release was prepared by G Mining Services and will be incorporated in an NI 43-101 technical report which will be available under the company's SEDAR+ profile, and on the company's website, within 45 days of this news release. The affiliation and areas of responsibility for each of the qualified persons involved in preparing the PEA, upon which the technical report will be based, are as noted herein.

Each QP has reviewed and approved the content of this news release.

The company cautions that the results of the PEA are preliminary in nature and include 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. There is no certainty that the results of the PEA will be realized.

Data verification

The qualified persons responsible for the preparation of the PEA and the technical report in respect thereof have verified the data disclosed in this news release, including sampling, analytical and test data underlying the information contained in this news release. Geological, mine engineering and metallurgical reviews included, among other things, reviewing mapping, core logs and relogging existing drill holes, review of geotechnical and hydrological studies, environmental and community factors, the development of the life-of-mine plan, capital and operating costs, transportation, taxation and royalties, and review of existing metallurgical test work. In the opinion of the qualified persons, the data, assumptions and parameters used to estimate mineral resources and mineral reserves, the metallurgical model, the economic analysis, and the PEA are sufficiently reliable for those purposes. The technical report in respect of the PEA, when filed, will contain more detailed information concerning individual responsibilities, associated quality assurance and quality control, and other data verification matters, and the key assumptions, parameters and methods used by the company.

Total cash costs and total cash costs per gold ounce

Total cash costs are reflective of the cost of production. Total cash costs reported in the PEA include mining costs, processing, water and waste management costs, on-site general and administrative costs, treatment and refining costs, royalties, and silver stream credits. Total cash costs per ounce is calculated as total cash costs divided by total LOM recovered gold ounces.

All-in sustaining costs and AISC per gold ounce

AISC is reflective of all of the expenditures that are required to produce an ounce of gold from operations. AISC reported in the PEA includes total cash costs, sustaining capital and closure costs. AISC per ounce is calculated as AISC divided by total LOM recovered gold ounces.

Qualified person

Louis Martin, PGeo (OGQ 0364), a consultant of First Mining, is a qualified person for the purposes of NI 43-101, and he has reviewed and approved the scientific and technical disclosure contained in this news release.

About First Mining Gold Corp.

First Mining is a gold developer advancing two of the largest gold projects in Canada: the Springpole gold project in Northwestern Ontario, where it has commenced a feasibility study and permitting activities are continuing with a draft environmental impact statement (EIS) for the project published in June, 2022, and the Duparquet project in Quebec, a PEA-stage development project located on the Destor-Porcupine fault zone in the prolific Abitibi region. First Mining also owns the Cameron gold project in Ontario and a portfolio of gold project interests including the Pickle Crow gold project (being advanced in partnership with Auteco Minerals Ltd.), the Hope Brook gold project (being advanced in partnership with Big Ridge Gold Corp.) and a large equity interest in Treasury Metals Inc.

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