Highlights

  • Red Mountain shares jumped 16% on 5 February 2026, after acquiring the Thompson Falls antimony project.
  • The acquisition expands Red Mountain’s critical minerals footprint across the US and Australia.
  • Initial assays reported high antimony grades alongside gold mineralisation at the project.
  • The project sits adjacent to the United States’ only operating antimony smelter.

Red Mountain Mining Ltd (ASX:RMX) shares climbed 16% to AUD 0.029 on 5 February 2026, extending a one-year gain of around 190%. Today’s price movement followed the company’s announcement of a new acquisition in the United States, which placed the stock firmly in focus among ASX-listed critical minerals explorers.

The price reaction came after Red Mountain confirmed it had acquired the Thompson Falls Antimony Project; a high-grade antimony asset located on the Montana–Idaho border.

Thompson Falls Acquisition Draws Market Attention

Red Mountain announced the acquisition of the Thompson Falls Antimony Project, which is located adjacent to the operations of United States Antimony Corporation (NYSE:UAMY). UAMY operates the only antimony smelter in the United States, positioning the Thompson Falls project within a key area of the US critical minerals supply chain.

According to the company, the project lies within the same host stratigraphy and close to UAMY’s Stibnite Hill Mine, which is described as the second-largest known stibnite vein deposit in the United States. High-grade antimony mineralisation at Stibnite Hill has previously been mined and was restarted by UAMY in late 2025.

High-Grade Results from Historical Workings

Red Mountain reported that it has identified three historical underground mines and a pit within the Thompson Falls project area. Initial assay results from sampling returned high antimony grades, including intersections of 36.5% Sb with 0.48 g/t Au, 21.0% Sb with 0.65 g/t Au, and 13.7% Sb with 0.14 g/t Au.

The company also noted that the project is prospective for silver, as it sits at the eastern end of Idaho’s Coeur d’Alene mineral district. This district has historically accounted for approximately 18% of total accumulated US silver production between 1884 and 2020, alongside significant production of lead, zinc, gold, copper, and antimony.

 

Critical Minerals Context and Project Portfolio

The Thompson Falls Antimony Project is located around 4.2 kilometres from UAMY’s operations and is positioned in antimony and silver, both of which are designated as critical minerals in the United States. The update coincided with the launch of a USD 12 billion US Government strategic minerals stockpile initiative aimed at securing critical mineral supply chains.

Red Mountain stated that the acquisition adds to its existing critical minerals portfolio across Utah, Idaho, and New South Wales. The company continues exploration and development activities at the Armidale Project in NSW, as well as progressing technical work at its Utah and Idaho projects.

Next Steps Outlined

Red Mountain expects to receive additional assay results from Thompson Falls sampling completed during the current quarter. Planned work includes further reconnaissance exploration, additional sampling, and inspections of identified underground mine workings to better understand mineralisation before finalising drill target plans.

 

FAQ Section

Why did Red Mountain Mining shares rise on 5 February 2026?

The shares rose after Red Mountain announced the acquisition of the Thompson Falls Antimony Project in the United States.

What is notable about the Thompson Falls Antimony Project?

The project is located adjacent to the United States’ only antimony smelter and hosts historical high-grade antimony mineralisation.

What are the next step for the Thompson Falls project?

Red Mountain expects additional assay results this quarter and plans further sampling and reconnaissance exploration.