Acquisition of “Thompson Falls” High-Grade Antimony Project Adjacent to America’s only Antimony Smelter

Red Mountain Mining Limited (ASX: RMX, US CODE: RMXFF, or “Company”), a Critical Minerals exploration and development company with an established portfolio in Tier-1 Mining Districts in the United States and Australia, is pleased to announce the Company’s newly-acquired Thompson Falls Antimony Project, (Figure 1), located 4.2km from United States Antimony Corporation’s operations (NYSE: UAMY; Market Cap A$2.2 billion) with the only operating Antimony smelter in the US – the Thompson Falls Smelter in Montana and the Stibnite Hill Mine. Red Mountain’s initial batch of assay results have returned outstanding grades of up to 36.5% Antimony and 0.65g/t Gold at the Thompson Falls Antimony Project.

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HIGHLIGHTS:

• Red Mountain has acquired the “Thompson Falls Antimony Project” adjacent to United States Antimony Corporation’s operations (NYSE: UAMY, Market Cap A$2.2b), which has the only Antimony smelter in the United States, and is crucial to the US Critical Minerals supply chain
• Red Mountain has immediately identified standout prospectivity at the project, locating three historical underground mines and a pit within the project area. Initial assays from the Thompson Falls Antimony Project have returned superb high-grade results including:
  • 36.5% Sb and 0.48g/t Au
  • 21.0% Sb and 0.65g/t Au
  • 13.7% Sb and 0.14g/t Au
• The Project is located on the Montana-Idaho border, within the same host stratigraphy and near UAMY’s Stibnite Hill Mine, the second largest known stibnite vein deposit in the US, where high grade antimony mineralisation has been previously mined, and restarted by UAMY in late 2025 in response to the severe supply shortage in the United States
• The Project is also highly prospective for Silver as it lies at the eastern end of Idaho’s Coeur d’Alene mineral district, which has accounted for ~18% of the USA’s total accumulated silver production, of over 1.25 billion ounces of silver between 1884 and 2020, along with 7.8Mt Lead, 3.0Mt Zinc, 1.1Moz Gold, 191kt Copper and 160kt Antimony
• Thompson Falls Antimony Project further strengthens Red Mountain's Utah, Idaho and NSW Critical Minerals portfolio, creating a unique Western asset base positioned to benefit from unprecedented US and Australian government support as both nations seek to secure supply
• The US Government this week launched a $12 billion strategic minerals stockpile initiative, aimed at securing Critical Mineral supply chains. Red Mountain's Thompson Falls Antimony Project, located 4.2km from UAMY’s operations, is well positioned in Antimony and Silver - both federally designated Critical Minerals aligned with US supply chain priorities
• Red Mountain continues to accelerate its Critical Minerals exploration and development at the Armidale project in NSW, Australia and additional technical work is rapidly progressing at the Company’s Utah and Idaho projects

Figure 1: Thompson Falls Antimony Project & High-Grade Antimony and Gold Samples, next to NYSE: UAMY’s Thompson Falls Smelter and Stibnite Hill Mine

Click here for the full ASX Release

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