American Tungsten & Antimony Commences Wet Table Trials at Del Sol Refinery

American Tungsten & Antimony (ASX: AT4) has begun wet table trials on tungsten and antimony mineralisation at the Del Sol refinery in Nevada as it works toward a proposed 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 required ahead of a proposed APT circuit at Del Sol.

About three tonnes of stibnite-bearing material from the White Spar antimony mine has also reached Del Sol for trial work alongside samples and drill core from the Antimony Canyon project in Utah.

The programs remain at an early stage, with no test work results yet available and Del Sol not in commercial production, while completion of AT4’s proposed acquisition of Del Sol Refining Inc and White Spar remains subject to outstanding conditions.

Tungsten Trials to Shape Expansion

The tungsten program is testing gravity separation across different feed sources and crush and grind sizes 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, while also producing concentrate for laboratory-scale caustic leach and APT crystallisation work at Del Sol.

Engineering proposals have been received from several shortlisted firms for the proposed APT expansion, antimony flake capacity increase, and specialty antimony product circuits, with appointment of a preferred firm targeted 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."

Antimony Restart Nears

Wet table trials on White Spar material are intended to identify 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 as AT4 evaluates a potential second domestic antimony feed source.

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

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

Funding and Permitting Work

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$162m critical minerals initiative, although 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 as it presents 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.