Resolution Minerals Advances Antimony Trioxide Production and Processing at Antimony Ridge with US FAST-41 Permitting

High-Purity Antimony Trioxide Produced at Antimony Ridge

Resolution Minerals Ltd (ASX:RML) has successfully produced an intermediate antimony trioxide product from large stibnite samples extracted from the Antimony Ridge historical open pits in Idaho. The pyrometallurgical process, conducted by Kingston Process Metallurgy (KPM) in Ontario, yielded an antimony trioxide concentrate with 99.38% Sb2O3 purity, marking a significant milestone for the project’s metallurgical advancement.

This initial success sets the stage for further refining tests, with final product results expected in the coming weeks. The company is exploring conventional pyrometallurgy as the base-case processing technology and has engaged multiple third parties to assess processing options.

Hydrometallurgical Processing and Concentrate Development

Alongside pyrometallurgical work, Resolution is advancing hydrometallurgical test work at ANSTO in Australia, aiming to develop a modern processing hub for antimony as stibnite within the US. This is particularly notable given the current lack of modern antimony processing facilities in the country.

Concentrate test work is also progressing at IMO labs in Perth on antimony, tungsten, and gold-bearing samples, reflecting the polymetallic nature of the Horse Heaven Project. The company’s ambition is to integrate these critical metals supply chains locally, leveraging recently acquired infrastructure including the Johnson Creek Mill site, which offers power, water, and private land ownership, potentially fast-tracking processing development.

Extensive Vein Swarms and Strategic Permitting Boost

Recent 3D modelling has revealed an extensive network of antimony and silver-bearing veins and vein swarms spanning 1,000 by 700 metres, with historical mining returning exceptionally high-grade antimony consistently above 30% and up to 50% Sb. These findings underscore the expanding scale potential of the Antimony Ridge deposit.

Importantly, the project has secured FAST-41 Transparency Coverage from the US Government Permitting Council, a designation expected to accelerate permitting timelines for up to 250 drill holes and bulk sampling. This fast-track status reflects the project's strategic importance as a domestic source of critical antimony supply for defence, energy, and industrial applications.

This development complements the company’s broader Horse Heaven strategy, which includes significant gold and tungsten assets at Golden Gate and Golden Gate South, where a major diamond drilling program is planned to commence in May 2026. The integration of these assets positions Resolution to supply multiple critical minerals from central Idaho.

The recent metallurgical progress and permitting acceleration follow the company’s earlier extensive high-grade antimony vein system announcement, reinforcing the potential scale and strategic value of the Antimony Ridge project.

Historical Significance and Future Development Plans

Antimony Ridge holds historical significance as a major antimony source during World War I, World War II, and the Korean War, with the district once producing over 90% of US antimony. Its proximity to Perpetua Resources’ Stibnite Gold Project, a recently permitted antimony-gold operation, adds regional context to Resolution’s ambitions.

Looking ahead, Resolution plans a significant bulk sampling program and an extensive drilling campaign of up to 250 holes pending regulatory approvals. These efforts aim to define the resource scale and support progression towards a maiden Mineral Resource Estimate, underpinning the development of a critical minerals supply hub in the US.