I-80’s Granite Creek resources triple: cost and cashflow lens for mine planners
Reviewed by Tom Sullivan

First reported on MINING.com
30 Second Briefing
I-80 Gold’s latest feasibility study for the Granite Creek underground mine in Nevada triples measured and indicated resources to 3.73 million tonnes at 7.17 g/t (859,500 oz.) and defines initial reserves of 2.2 million tonnes at 7.87 g/t (556,500 oz.), but lifts life-of-mine all-in sustaining costs 42% to $2,273/oz. Total capital and closure costs rise to $145 million, including $83 million sustaining and $49 million for refurbishing the Lone Tree plant, which is expected online in late 2027. The 8.5-year plan targets 75,000 oz./year from 2028–32, with Granite Creek ore feeding the refurbished Lone Tree autoclave and forecast net cash flow of $238 million over that five-year period.
Technical Brief
- Feasibility study assumes base-case gold price of US$2,750/oz, yielding after-tax NPV of US$118 million.
- Using a US$3,000/oz gold price, NPV is US$193 million versus US$373 million in the 2025 PEA sensitivity.
- Total capital and closure costs increase from US$112 million in the PEA to US$145 million in the feasibility.
- Closure and reclamation are budgeted at US$12.7 million within the Granite Creek life-of-mine plan.
- Average metallurgical recovery improves from 78% in the PEA to 87%, lifting recovered ounces to 485,000.
- Granite Creek net cash flow is forecast at US$238 million from 2028–32, including US$92 million in 2028 alone.
- Company-level financing of US$500 million underpins staged growth to 300,000–400,000 oz/year by 2031, funding a third-stage Mineral Point open pit.
- Until Lone Tree starts in Q4 2027, Granite Creek ore will use third-party processing with some stockpiling ahead of autoclave commissioning.
Our Take
Our coverage shows relatively few Nevada gold developers combining underground mines with refurbished central plants like Lone Tree; this hub-and-spoke approach can improve recoveries and mine life flexibility at Granite Creek but tends to concentrate technical and schedule risk into the 2027 commissioning milestone.
The earlier termination of Vox Royalty’s offtake over Granite Creek and Ruby Hill gives i-80 more marketing flexibility for future Nevada gold output, which becomes more important as the company targets 300,000–400,000 oz/year by 2031 under a capital structure already layered with royalty and prepay obligations.
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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