Resolution Minerals (ASX: RML) has reported exceptional high-grade antimony, silver, and gold results from a recently completed rock sampling program at the historical Antimony Ridge Mine, part of its Horse Heaven Project in Idaho, United States.
The company announced assays of up to 48.7 per cent antimony and 890 grams per tonne (g/t) silver from the program, confirming widespread, very high-grade antimony mineralisation at surface.
These results reinforce Horse Heaven’s potential as a strategically significant domestic source of antimony, a critical mineral highlighted by U.S. authorities for its importance in defence, energy storage, and advanced manufacturing.
Antimony Ridge lies immediately adjacent to Perpetua Resources’ Stibnite Gold Project, a large and recently permitted antimony-gold development that underscores the geological and strategic importance of this district.
Outstanding antimony and silver grades were recorded from five massive stibnite samples — an antimony sulphide mineral — collected in October 2025 from the historical Antimony Ridge Mine.
The results were as follows:
- Sample 732005: 48.7% Sb, 270 g/t Ag and 0.69 g/t Au
- Sample 732006: 35.5% Sb, 223 g/t Ag and 1.07 g/t Au
- Sample 732007: 42.0% Sb, 200 g/t Ag and 0.85 g/t Au
- Sample 732008: 37.9% Sb, 890 g/t Ag and 0.81 g/t Au
- Sample 732009: 31.7% Sb, 567 g/t Ag and 1.19 g/t Au
The five rock samples averaged 39.2 per cent antimony and 430 g/t silver, confirming consistently high-grade mineralisation and strong silver association across the zone.
The samples, each averaging approximately 3.6 kilograms, were significantly larger than standard rock chips and are considered representative of historical mineralisation within the system.
The latest assays build on earlier rock chip and soil sampling reported in September 2025, which delineated a wide antimony-gold-silver mineralised footprint at Antimony Ridge.
This new phase of sampling also supports Resolution’s broader initiative to collect about 100 kilograms of representative high-grade stibnite material for ongoing metallurgical test work.
Craig Lindsay, CEO of U.S. Operations, said the assay results validate the strength and scale of the target area.
“These results represent a significant validation of the Antimony Ridge Target and further demonstrate the exceptional grade potential of the Horse Heaven Project.
“Antimony grades of this magnitude are rarely reported globally, particularly exposed at surface, and the consistent association with strong silver and gold values materially enhances the project’s overall value proposition.
“Importantly, Antimony Ridge is emerging as a large, coherent, high-grade system within a strategically critical jurisdiction at a time when sure U.S. antimony supply has become a national priority.
“With metallurgical test work underway and permitting progressing toward drilling and bulk sampling, we believe Horse Heaven is rapidly advancing toward becoming a highly strategic U.S critical minerals asset.”
Resolution Minerals has submitted bulk stibnite samples to metallurgical laboratories in Canada and Australia for preliminary test work and mineralisation characterisation.
The company expects to report results from these studies as they become available.
In parallel with the metallurgical analysis, assay results are pending for the final diamond and reverse circulation drill holes completed during the 2025 drilling season at the Golden Gate target, another zone within the Horse Heaven Project.
