This report is based on public company disclosures, filings and announcements reviewed by GSN; figures are as stated by the company and have not been independently verified.

Tesoro Gold (ASX: TSO) announced the establishment of a maiden ore reserve at its Ternera gold deposit located in Chile. According to the company, the reserve contains 1.28 million ounces of gold contained within 42.8 million tonnes of material grading 0.93 grams per tonne. The announcement was reported by Small Caps on September 18, 2026.

The maiden ore reserve is derived entirely from the Measured and Indicated components of the mineral resource estimate released in August 2026. Tesoro Gold stated that the reserve represents approximately 87 percent of the 1.47 million ounces of gold contained in those resource categories. The company noted that no Inferred Mineral Resources were included in the reserve calculation.

The reserve is contained within a single open pit design. Tesoro Gold said the deposit supports a projected mine life of more than 13 years based on a planned processing rate of 3.0 million tonnes per annum. The average grade over the first 10 years of production is estimated at 1.16 grams per tonne. The reserve consists of 2.8 million tonnes of Proved Reserves grading 1.05 grams per tonne and 40.1 million tonnes of Probable Reserves grading 0.92 grams per tonne.

The company provided economic metrics from a pre-feasibility study for the El Zorro project, which includes the Ternera deposit. Using a gold price assumption of US$3,500 per ounce, Tesoro Gold reported a post-tax net present value of US$994 million and a post-tax internal rate of return of 57 percent. The study indicated a payback period of 17 months. Pre-production capital expenditure was estimated at US$276.5 million, with operating costs projected at US$1,538 per ounce of gold produced.

Tesoro Gold said the reserve provides the development base for the El Zorro project as the company advances a definitive feasibility study targeted for completion in calendar 2026. The company also stated that environmental and sectorial permit applications are approximately 75 percent complete. The full environmental impact assessment and closure plan are targeted for submission in the first quarter of 2027.

Metallurgical test work supported by the company indicates a conventional crushing, grinding, gravity, and carbon-in-pulp processing flowsheet. Testing showed gold extractions between 92.4 percent and 97.4 percent. Tesoro Gold adopted a design gold recovery of 94.5 percent for the reserve calculation.

Managing Director Zeff Reeves commented on the significance of the reserve. The company quoted him as saying the Ternera gold deposit represents a rare, single open-pit development opportunity in a world-class mining friendly country. He added that the company will continue advancing technical and development workstreams for El Zorro in parallel with drilling programs aimed at extending the existing resource.

For investors, this development marks a significant step in the project lifecycle, moving from resource estimation to defined reserves with positive economic indicators. The high conversion rate from resources to reserves suggests consistent mineralization, which can reduce exploration risk. The timeline for the definitive feasibility study and permit submissions will be critical for determining when the project might move toward construction.

Sources