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Highlights
- Resolution Minerals has produced a high-purity intermediate antimony trioxide product grading 99.38 wt% from stibnite samples at its Antimony Ridge site in Idaho.
- Pyrometallurgical test work is advancing, with further refining results expected soon.
- Parallel hydrometallurgical testing is underway at ANSTO to assess alternative processing routes.
- Antimony grades exceed 30% Sb and reach up to 50% in sampled stibnite veins.
- 3D modelling confirms a large-scale mineralised system with expansion potential.
- The Horse Heaven Antimony-Tungsten-Gold-Silver Project has received FAST-41 status to accelerate permitting.
- Bulk sampling and expanded drilling programs are planned to support resource growth.
Resolution Minerals Ltd (ASX:RML) (OTCQB:RLMLF) has reported encouraging developments at its Antimony Ridge site, Horse Heaven Project, in Idaho. The company has confirmed the production of an intermediate antimony trioxide product, along with advancements in both pyrometallurgical test work and hydrometallurgical processing at Antimony Ridge. These activities form part of a broader effort to advance the Horse Heaven Antimony-Tungsten-Gold-Silver Project.
Following the update, RML shares rose 13.11% to AUD 0.069 per share during morning trading on 14 April 2026. Over the past month, RML’s share price has surged 38% and 590% in last 12 months.
High-Purity Antimony Trioxide Produced
Large stibnite samples sourced from historical open pits at Antimony Ridge have been processed using conventional pyrometallurgical volatilisation techniques. This work, carried out by Kingston Process Metallurgy in Ontario, resulted in an intermediate antimony trioxide product with a recorded content of 99.38 wt%.
Further refining test work using pyrometallurgical methods is ongoing, with final product results anticipated in the coming weeks. Pyrometallurgy test work would provide the base-case data for processing antimony, and the company has also initiated discussions with third-party groups regarding potential processing arrangements based on this method.
Parallel Processing Pathways Under Evaluation
In addition to pyrometallurgy, hydrometallurgical test work is progressing on Antimony Ridge samples at ANSTO in Australia. Results from these tests are pending and are expected to inform future processing decisions.
At the same time, laboratory work at IMO facilities in Perth is examining methods to concentrate antimony ore, tungsten and gold-bearing materials. These parallel efforts are aimed at establishing a hydrometallurgical processing hub in Idaho, for antimony (in the form of stibnite), addressing the current shortage of modern antimony processing facilities in the country.
Resource Potential and Historical Context
Recent test work on antimony-bearing stibnite veins has returned antimony grades consistently above 30%, with some results reaching up to 50% Sb. These veins were historically mined during World War I, World War II, and the Korean War.
Three-dimensional modelling of numerous antimony and silver-bearing veins, stockworks and veins swarms across an area measuring approximately 1,000 metres by 700 metres indicated a large-scale deposit with scope for further expansion at Antimony Ridge. Details Here.
Antimony Ridge – As part of Resolution’s larger Horse Heaven Project. Image source: Company update
Permitting and Strategic Developments
The Horse Heaven Project has been selected for FAST-41 Transparency Coverage by the U.S. Permitting Council. This development is expected to streamline permitting timelines for proposed activities, including up to 250 drill holes and bulk sampling programs.
The company is also considering the development of a hydrometallurgical processing hub in Idaho, citing limited modern antimony processing infrastructure within the US.
Upcoming Exploration and Project Plans
Resolution Minerals plans to initiate a bulk sampling program targeting high-grade antimony ore, subject to approvals. In addition, a Phase 2 drilling campaign is scheduled to begin in May 2026 at the Golden Gate project, with up to 45,000 feet of diamond core drilling planned. The program aims to define the extent of gold and tungsten mineralisation and support future resource estimation work.
Ongoing metallurgical testing, combined with exploration and modelling activities, continues to shape development plans at Antimony Ridge. With multiple processing methods under review and expanded sampling programs planned, the project remains a central component of Resolution Minerals’ broader strategy within the Horse Heaven project area.
