Minera Alamos’ Copperstone gold mine: project economics and design notes for engineers
Reviewed by Joe Ashwell
First reported on MINING.com
30 Second Briefing
Minera Alamos has approved a US$58 million build-out of the past-producing Copperstone underground gold mine in Arizona, targeting about 46,000 oz. per year over a six-year life at an all-in sustaining cost of US$1,314/oz and payback in roughly 1.2 years. The new PFS, based on 4.1 million measured and indicated tonnes at 4.83 g/t (630,000 oz contained), gives an after-tax NPV of US$374 million and IRR of 108% at US$3,500/oz gold, rising to US$537 million NPV and 154% IRR at US$4,500/oz. Copperstone, on the Walker Lane structural trend and already permitted with existing underground development and processing infrastructure, will be funded from cash, a US$75 million revolver and Pan mine cash flow, with first production aimed for mid-2027 and further underground, down-plunge and potential open-pit heap-leach expansion drilling planned.
Technical Brief
- Initial construction capex is US$58 million, with an additional US$77 million sustaining capital post-start-up.
- Funding stack combines US$46 million cash (March balance), a US$75 million revolver and Pan mine cash flow.
- PFS economics use a 5% discount rate, yielding IRRs above 100% at modelled gold prices.
- Resource update (1 Dec) reports 4.1 Mt measured and indicated at 4.83 g/t plus 0.4 Mt inferred at 4.04 g/t.
- Current reserves account for only ~50% of measured and indicated resources, leaving material conversion potential.
- Down-plunge extensions will be drilled from underground, indicating planned step-out development beyond existing workings.
- Additional open-pit potential is being evaluated for a standalone heap-leach operation, separate from underground mining.
- The 37 km² property on the Walker Lane trend includes legacy underground development, processing plant and existing permits, reducing schedule risk.
Our Take
Minera Alamos’ role at both Copperstone in Arizona and the Pan mine in Nevada (where Turner Mining Group recently mobilised a new Caterpillar fleet under a multi-year contract) suggests the company is positioning itself as an operator with a contiguous footprint along the Walker Lane trend, which can simplify contractor relationships and equipment deployment across sites.
With Copperstone’s relatively short six-year mine life but very high IRR at current gold price assumptions, the project looks geared more as a fast-payback cash generator that can help fund Minera Alamos’ Mexican assets such as Santana, Cerro de Oro and La Fortuna, rather than as a long-life standalone cornerstone mine.
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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