McEwen’s Grey Fox PFS: mine-life, capex and return insights for gold planners
Reviewed by Tom Sullivan

First reported on MINING.com
30 Second Briefing
McEwen Mining’s pre-feasibility study for the Grey Fox underground project near Timmins, Ontario, outlines 87,000 oz/y of gold output from 2028–2041, peaking at 100,000 oz in 2029, extending the Fox Complex mine life by 15 years and feeding the existing Stock mill with 87.5% projected recovery. The $181 million initial capex project, based on 18.8 Mt at 3.28 g/t Au (nearly 2 million oz indicated, 980,000 oz in reserves), shows a post-tax NPV5 of $282 million, 25% IRR and 4.6-year payback at $3,000/oz gold. Two independent portal-accessed underground operations are planned, with construction targeted for spring 2027 and commercial production in 2029, plus a $5 million drilling programme to convert remaining resources.
Technical Brief
- Mining layout comprises two independent underground operations, each accessed via its own surface portal.
- Ore from Grey Fox will be truck-hauled to surface, then road-hauled to the existing Stock mill for processing.
- Stock mill feed will be blended with material from the operating Stock mine, implying coordinated grade and throughput control.
- All-in sustaining cost is projected at US$2,212/oz over life-of-mine, framing operating margin sensitivity to gold price.
- Indicated resource underpinning the PFS totals 18.8 Mt at 3.28 g/t Au, nearly 2 Moz contained.
- Proven and probable reserves of 980,000 oz represent only ~40% of Grey Fox’s total current resource inventory.
- McEwen has allocated US$5 million for additional drilling focused on resource-to-reserve conversion and mine plan optimisation.
- Pre-production work includes detailed engineering, long-lead procurement, and amendments to both water permit and closure plan.
Our Take
Recent coverage of McEwen shows strong cash inflows from the San José gold-silver mine in Argentina and rising Q1 2026 gold revenues, which likely improves the company’s capacity to fund the US$181 million initial capital at Grey Fox without relying solely on dilutive equity.
In our database, McEwen also appears in several copper-focused pieces via McEwen Copper and the Los Azules financing push, so committing a further US$5 million drilling budget at the Grey Fox gold deposit suggests management is still prepared to allocate meaningful exploration capital to precious metals alongside its large copper growth option.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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