• Near-surface drilling delivers multiple positive gold intercepts highlighted by DUP25-064, which returned 3.23 g/t Au over 25.9 m, including 11.20 g/t Au over 2.0 m, and including 10.16 g/t Au over 1.4 m, extending mineralization to 100 m depth following previously delineated 100 m strike extension
• First Mining continues to test and advance the Miroir target mineralization controls with 20 holes and ~4,450 m completed to date

VANCOUVER, BC, Sept. 24, 2025 /PRNewswire/ – First Mining Gold Corp. (“First Mining” or the “Company”) (TSX: FF) (OTCQX: FFMGF) (FRANKFURT: FMG) is pleased to announce additional drilling results from the 2025 drilling program at its Duparquet Gold Project (“Duparquet Project” or the “Project“) located in the Abitibi region of Quebec, Canada. The Company is actively drilling at the Duparquet Project through to the fall and has completed ~16,000 m of drilling to date, with a continued focus on advancing potential resource growth targets. Since the initial discovery (see January 2025 news release), a total of 20 holes have been drilled at Miroir, with assay results from some of these holes already disclosed. Assay results from the remaining 13 holes drilled at Miroir as part of the 2025 program are pending. The Company will provide further updates as results are received and interpreted.

Drilling at the Miroir target, located 225 m north of the Central Duparquet – Valentre – Dumico (“CVD“) target, continues to build strong continuity, returning multiple robust gold intercepts near surface. Assay results from drill hole DUP25-064 returned 3.23 g/t Au over 25.9 m, including 11.20 g/t Au over 2.0 m, and including 10.16 g/t Au over 1.4 m. Drill hole DUP25-066, which is a 45 metre step-out to the east of DUP25-064, returned 1.37 g/t Au over 30.6 m, including 2.56 g/t Au over 4.0 m, and including 2.55 g/t Au over 6.6 m. These latest drilling results further support the continuity of near-surface higher-grade mineralization and extends the Miroir target to a vertical depth of 100 m below surface, where it remains open both up-dip toward surface and at depth (Figure 1).

“The Miroir target continues to deliver new discoveries within the largely underexplored volcanic setting of the Duparquet Project,” stated Dan Wilton, CEO of First Mining. “The strong grades and widths encountered to date provide new and exciting opportunities in our review of development scenarios that can now include near-surface, higher grade mineralization potential.”

The Miroir target is intersecting significant near-surface mineralization and this target represents an excellent opportunity for expansion in this area (Figure 2). Interpreted as a folded structure from the 3D geological model and airborne geophysics, the Miroir target is being drill tested to evaluate the near-surface and down-plunge extent of mineralization. Notably, the Miroir host lithologies have a strong affinity towards brecciated and altered mafic volcanic host lithologies, occurring within a volcanic sequence in close proximity to syenite intrusive units. Recent exploration success at Miroir continues to highlight this area together with the CVD and Aiguille targets as an emerging cluster of potential resource growth centres with synergies for future mining development.

The latest reported assays represent approximately 600 m of drilling from a total of ~4,450 metres across 20 drill holes. These holes were focused on advancing the understanding of mineralization controls at the Miroir target. Assay highlights are provided in Table 1, with the full list of assay results in Table 2 and drill collar details in Table 3.

Further drill testing ongoing at the Miroir target where assays are pending is shown in Figure 1. As results are returned and reviewed, First Mining will continue to interpret and evolve the geological understanding of the area for further drill advancement.

Table 1: Significant 2025 Drill Intercepts from the Miroir Target

Duparquet 2025 Exploration Program Updates

Exploration activities at the Duparquet Project continue to advance, with more than 16,000 m drilled to date in 2025. Drilling remains focused on key resource expansion targets including CVD, Miroir, Aiguille, North Zone, South Zone, and the Minuit Zone, where programs are aimed at building on the Project’s strong growth potential (Figure 3). In parallel, regional field programs are progressing to refine and advance additional targets toward future drill readiness.

Additional Details on the Miroir Target

The most recent 2025 drilling at the Miroir target focused on further delineating the extent of near-surface mineralization discovered in 2024 with drill hole DUP24-048 returning 3.12 g/t Au over 19.35 m (see news release dated January 20, 2025). Earlier drilling this year, including drill hole DUP25-052, returned a further intercept along strike of 2.77 g/t Au over 11.1 m, including 4.36 g/t Au over 6.5 m (see news release dated May 28, 2025), demonstrating encouraging grades and widths within this shallow target. The most recent drilling continues to confirm and expand the Miroir target, extending mineralization to a vertical depth of 100 m below surface and highlighting multiple near-surface gold zones (Figures 4 and 5).

The interpreted geophysical fold target has now been expanded to a strike length of 140 m, reinforcing the shallow, high-potential nature of the target and its ongoing growth potential. Notable results from the most recent drilling include drill hole DUP25-064, which returned 4.64 g/t Au over 4.6 m, including 6.3 g/t Au over 2.4 m, as well as 3.23 g/t Au over 25.9 m, including 11.2 g/t Au over 2.0 m and 10.16 g/t Au over 1.4 m, and 4.15 g/t Au over 7.4 m, including 8.72 g/t Au over 3.0 m. Drill hole DUP25-066 returned 0.64 g/t Au over 22.0 m and 1.37 g/t Au over 30.6 m, including 2.56 g/t Au over 4.0 m, while DUP25-067 returned 2.58 g/t Au over 4.0 m. These results continue to demonstrate the multiple, high-quality gold zones within the Miroir target and reinforce its potential for further expansion.

Mineralization at the target area is typically associated with syenite-basalt contacts. Mineralization in the most recent drill holes is hosted within brecciated silica-altered syenite and basalt, with up to 10% very fine-grained disseminated pyrite mineralization, and is associated with smoky dark quartz veinlets. The mineralized intercepts are spatially correlated with D2 deformation zones and coincident with a geophysical inferred folded basalt-syenite contact that is striking northeast to southwest and plunging towards the east. Further validation and refinement is planned to test the plunge dip directions and stratigraphic controls on mineralization in this area.

Table 2: Latest Assay Results from 2025 Drill Program

Table 3: 2025 Drill Hole Locations, Miroir Target

About the Duparquet Gold Project

The Duparquet Project is geologically situated in the southern part of the Abitibi Greenstone Belt and is geographically located approximately 50 km north of the city of Rouyn-Noranda. The Project benefits from easy access and proximity to an existing workforce and infrastructure, including road, rail and hydroelectric grid power. The Duparquet Project currently hosts an NI 43-101 compliant gold resource of 3.44 million ounces in the Measured & Indicated category, grading 1.55 g/t Au, and an additional 2.64 million ounces in the Inferred category, grading 1.62 g/t Au. First Mining completed a Preliminary Economic Assessment¹ (“PEA“) on the Project in 2023.

The Duparquet Project totals approximately 5,800 hectares focused on an area of 19 km of strike length along the prolific Destor-Porcupine Fault Zone, along with numerous mineralized splays and influential secondary lineaments. The Duparquet Project includes the past-producing Beattie, Donchester and Duquesne mines as well as the Central Duparquet, Dumico and Pitt Gold deposits.

Analytical Laboratory and QA/QC Procedures

All sampling completed by First Mining within its exploration programs is subject to a Company standard of internal quality control and quality assurance (QA/QC) programs which include the insertion of certified reference materials, blank materials and a level of duplicate analysis. Core samples from the 2025 drilling program at Duparquet were sent to AGAT Laboratories, with sample preparation in Val d’Or, Quebec and analysis in Thunder Bay, Ontario, where they were processed for gold analysis by 50 gram fire assay with an atomic absorption finish. Samples from selected holes were sent to AGAT Laboratories in Calgary, Alberta, for multi-element analysis (including silver) by inductively coupled plasma (ICP) method with a four acid digest. AGAT Laboratories systems conform to requirements of ISO/IEC Standard 17025 guidelines and meets assay requirements outlined for NI 43-101.

Qualified Person

James Maxwell, P.Geo., VP, Exploration and Project Operations for First Mining, is a “Qualified Person” for the purposes of NI 43-101 Standards of Disclosure for Mineral Projects and 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 we have commenced a Feasibility Study and permitting activities are on-going with a final Environmental Impact Statement / Environmental Assessment for the project submitted in November 2024, and the Duparquet Gold 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 30% project interest in the Pickle Crow Gold Project.

First Mining was established in 2015 by Mr. Keith Neumeyer, founding President and CEO of First Majestic Silver Corp.

ON BEHALF OF FIRST MINING GOLD CORP.

Daniel W. Wilton
Chief Executive Officer and Director