AT4 Wet-Table Trials at Del Sol Target APT, Antimony Restart

American Tungsten & Antimony (ASX: AT4) has started wet table trials on tungsten and antimony material at the Del Sol refinery in Nevada. The company is working toward an expansion into ammonium paratungstate (APT) production and a restart of the existing antimony flake circuit.

Scheelite-bearing material from the Dutch Mountain tungsten project in Utah and nearby third-party sources is being tested to establish the concentration step needed before a proposed APT circuit at Del Sol. About three tonnes of stibnite-bearing material from the White Spar antimony mine has also reached the site for trial work alongside samples and drill core from the Antimony Canyon project in Utah.

The programs remain early. No test work results are available yet and Del Sol is not in commercial production. Completion of AT4's proposed acquisition of Del Sol Refining Inc and White Spar remains subject to outstanding conditions.

The tungsten program is testing gravity separation across different feed sources and crush and grind sizes. The goal is to determine concentrate grade, recovery, optimum liberation size, and whether additional upgrading steps may be required.

AT4 expects the resulting data to help define the engineering basis for the front-end gravity circuit and downstream APT circuit. The work should also produce concentrate for laboratory-scale caustic leach and APT crystallisation trials at Del Sol.

Engineering proposals have come in from several shortlisted firms for the proposed APT expansion, antimony flake capacity increase, and specialty antimony product circuits. AT4 expects to appoint a preferred firm within two weeks.

“AT4 is entering into an exciting phase,” chief executive officer Casper Adson said. “The engaged consultants, metallurgists, and engineers at Del Sol are working alongside our team on the preparation for upcoming trials to identify the fastest and most efficient path forward for both circuits to enable Del Sol to be expanded.”

Wet table trials on White Spar material are designed to find an efficient route for upgrading run-of-mine material into stibnite concentrate before it enters Del Sol's existing alkaline leach and electrowinning circuit. AT4 expects concentration before leaching to reduce reagent use, residence time, and unit operating costs while increasing the effective throughput capacity of the permitted antimony plant.

Material from the Antimony Canyon project is being tested in parallel to assess its compatibility with the Del Sol flowsheet and establish its concentration response. AT4 is evaluating Antimony Canyon as a potential second domestic antimony feed source.

The concentration work is the immediate precursor to a full restart trial of the antimony flake circuit. AT4 is targeting that restart to begin by the end of the September quarter 2026.

The restart is intended to generate verified operating data across throughput, recovery, reagent consumption, power draw, and product specification. That data would feed into engineering, specialty product development, prospective offtake discussions, and applications under US federal critical minerals programs.

AT4 was shortlisted on 18 August by the United States Department of Energy (DoE) to begin negotiations over a potential financial award of up to US$18 million under a US$162 million critical minerals initiative. No funding agreement has been secured.

Beyond the DoE shortlist, AT4 plans meetings at the White House in Washington DC and in New York with potential strategic stakeholders. The company is presenting Del Sol as a domestic refining asset for tungsten and antimony.

“AT4 is not aware of any other US company with refining infrastructure and domestic feed for both of these metals, and it intends to be the first to bring them into production,” executive chair Tim Morrison said.

AT4 is also progressing applications with the Nevada Division of Environmental Protection to expand permitted feed capacity to 100,000 tons per year and extend the permit scope to tungsten refining.