Red Mountain Mining (ASX: RMX) has expanded its Yellow Pine Antimony Project in Idaho’s Stibnite mining district, increasing the project area by 75% after acquiring additional claims immediately northeast of its existing holdings.
The expansion follows a September field mapping program that confirmed highly prospective geology across the tenure, strengthening Red Mountain’s position within one of the most strategically important critical mineral districts in the US.
The enlarged project – which now covers 426 hectares – sits less than 2 kilometres from Perpetua Resources’ 4.8-million-ounce gold and 148-million-pound antimony reserve at the Stibnite project, and about 5km south of Resolution Minerals’ Horse Heaven discovery.
Key Structural Corridor
Red Mountain said the newly acquired ground captures the northeast continuation of a major regional fault that hosts key controls on gold and antimony mineralisation at Stibnite and Horse Heaven, while field mapping confirmed multiple breccia zones and identified two small historic workings targeting quartz–sulphide veins prospective for antimony and gold.
The structural setting, host rock sequence and surface indications all mirror those associated with major intrusion-related gold–antimony deposits elsewhere in the district.
The Stibnite district has long been recognised as the largest known antimony centre in the US, with historic Yellow Pine and Hangar Flats mining delivering nearly 40,000 tonnes of antimony between 1932 and 1952.
Perpetua has commenced early works on its development, supported by more than US$330 million in recent strategic investments.
To the west, Resolution Minerals recently reported substantial gold intercepts at Golden Gate, including 189.2 metres at 1.30 grams per tonne gold and 265.2m at 0.60g/t gold from surface, reinforcing the district’s strong geological continuity.
Mapping and Sampling Work
Red Mountain’s upcoming work at Yellow Pine will focus on mapping and sampling along the main northeast-striking fault and the granite–metasediment, using the results to define initial drill targets across the expanded tenement position.
The project forms part of Red Mountain’s growing portfolio of critical mineral assets in Tier 1 US jurisdictions, including its Utah and Silver Dollar antimony projects.
Unprecedented shortages in Western supply of strategic metals — coupled with strong policy support in both the US and Australia — continue to reinforce the company’s strategy to build a portfolio of advanced critical minerals projects.
Red Mountain is actively engaging with potential US strategic partners to support project development pathways and access government funding programs designed to boost domestic supply chain resilience.
The expanded Yellow Pine footprint now offers it a more robust exploration foundation in one of North America’s most prospective gold–antimony districts.
