ASX: AT4 | OTCQB: ATALF | 22 August 2026
AT4 Commences Wet Table Trials at Del Sol as Tungsten and Antimony Refining Pathways Advance
American Tungsten & Antimony Limited has commenced wet table gravity concentration trials at the Del Sol hydrometallurgical refinery in Amargosa Valley, Nevada, on both scheelite-bearing tungsten mineralisation and stibnite-bearing antimony mineralisation. The work programs are directed at two objectives: establishing the front-end concentration step required to expand Del Sol into ammonium paratungstate production, and optimising antimony concentration ahead of a full restart trial of the refinery’s existing alkaline leach and electrowinning circuit.
What Has Changed
Three days after being shortlisted by the US Department of Energy, AT4 has moved from stated strategy to physical work at the refinery. Material is on site, trials are running, and the engineering process is at the appointment stage.
The Two Work Streams
Ammonium paratungstate is the essential commercial intermediate for tungsten metal powder and tungsten carbide. There is currently no meaningful domestic United States APT production capability. Del Sol is a constructed and permitted hydrometallurgical facility which, subject to technical verification, already contains unit operations required for the front-end processing of scheelite concentrate into APT.
Beneficiation of scheelite into a concentrate is required ahead of any APT circuit. Scheelite responds strongly to gravity separation because of its high specific gravity, so AT4 has prioritised wet table trials as the first physical work stream of the APT expansion, running in parallel with the engineering study process.
Feed is being drawn from the Dutch Mountain Tungsten Project in Utah, the project intended to feed the Dutch Mountain Tungsten Concentrator under the Company’s hub and spoke strategy, together with external third-party tungsten sources in the southwestern United States. The Company regards third-party feed as strategically important for three reasons: it demonstrates Del Sol sits within a catchment of domestically sourced tungsten material, it allows the refinery to be commissioned and optimised ahead of AT4’s own mine development timelines, and it provides feed variability for the engineering design basis.
Approximately three tonnes of stibnite-bearing mineralisation has been extracted from the existing small scale extraction zone at White Spar and hauled to Del Sol. The haulage confirms, on a practical operating basis, the logistics chain between mine and refinery that underpins the Company’s mine to metal strategy. Samples and drill core from Antimony Canyon are being processed in parallel to confirm metallurgical compatibility with the Del Sol flowsheet.
The objective mirrors the tungsten program: upgrade run of mine material into a stibnite concentrate before it is fed to the refinery, rather than treating unconcentrated ore. Gravity concentration ahead of the leach circuit is expected to reduce reagent consumption, residence time and unit operating cost per tonne of contained antimony, and to increase the effective antimony throughput capacity of the existing permitted plant.
Concentrate is then intended to be fed through the facility’s existing alkaline leach and electrowinning process to produce electrolytic antimony flake. That route is strategically significant because it processes stibnite without generating SO2 gas, avoiding the dedicated capture and abatement infrastructure required by conventional smelting.
Two applications are being progressed with the Nevada Division of Environmental Protection. The first seeks to expand permitted feed capacity to 100,000 tons per year. The second seeks to extend the Del Sol permit scope to tungsten refining, and will be progressed in parallel with the engineering work.
AT4 believes that if the tungsten permit extension is granted, Del Sol would be the only refinery in the United States capable of producing both tungsten and antimony products. The permit application has not been submitted for determination and there is no certainty that it will be granted.
What the Wet Table Program Is Designed to Establish
The program tests various feed sources across a range of crush and grind sizes. Select each outcome to expand.
The trials have commenced and no samples have yet been submitted for assay. No testwork results are reported in the Company’s announcement. AT4 has stated it will report the outcomes of the program to the market once results have been received, compiled and reviewed.
Engineering and the Route to Non-Dilutive Funding
Requests for proposal were issued to five leading international engineering firms covering the proposed APT circuit at Del Sol, the expansion of antimony flake capacity and the addition of specialty antimony product circuits. Several proposals have been received. AT4 expects to complete its assessment and engage the preferred firm within the next two weeks.
The appointed firm will be scoped to deliver a design basis together with capital and operating cost estimates for a domestic United States APT refinery at Del Sol. The Company has stated that a defined, engineered and costed APT pathway is the technical foundation on which it intends to pursue non-dilutive United States debt and government funding programs.
That connects directly to the DOE shortlisting announced on 18 August 2026, under which AT4 was selected as one of nine projects nationally to commence negotiations on a potential award of up to US$18 million from a US$162 million federal initiative. Grant and loan programs of that type require an engineered basis of estimate. The engineering appointment is the step that produces it.
The Regulatory Driver
Executive Chair Tim Morrison framed the commercial case in the announcement, noting that the United States has no meaningful domestic production of either tungsten or antimony, and that Executive Order 14415 and the prohibition taking full effect on 1 January 2027 mean the defence industrial base has to find compliant domestic sources. Morrison stated that Del Sol is built, permitted, and has sources of United States tungsten and antimony today.
On the DOE shortlisting, Morrison said the selection confirms where United States Government investment is heading, being towards domestic mining, processing and manufacturing capacity across critical mineral supply chains, and that this is precisely what AT4 is building. He added that, on the basis of publicly available information, AT4 is not aware of any other United States company with refining infrastructure and domestic feed for both metals, and that the Company intends to be the first to bring them into production.
Chief Executive Officer Casper Adson said AT4 is entering an exciting phase, with tungsten and antimony samples from both internal and nearby third-party sources being processed at Del Sol to determine optimum conditions for the production of both tungsten APT and antimony flake, and that the engaged consultants, metallurgists and engineers are working alongside the AT4 team to identify the fastest and most efficient path forward for both circuits.
Restart Trial and Specialty Products
The concentration trials are the immediate precursor to a full restart trial of the Del Sol antimony flake circuit, targeted to commence by the end of the current quarter. The restart trial is intended to generate verified operating data across throughput, recovery, reagent consumption, power draw and product specification.
AT4 has stated those results are intended to feed four separate work streams: the capacity expansion engineering, the specialty product development program covering Regulus II antimony metal ingot, antimony trisulphide and sodium antimonate, commercial discussions with prospective offtake counterparties, and applications under United States federal programs supporting domestic critical minerals capability.
Strategic Engagement in Washington D.C. and New York
Chief Executive Officer Casper Adson, together with the Nexus Metals team, will be in Washington D.C. and New York next week for a program of meetings with potential strategic stakeholders. The stated aim is to introduce Del Sol as a constructed and permitted domestic refining asset and to accelerate the development pathway for both APT and antimony refining at the facility.
AT4 has been explicit about the limits of that engagement. Beyond the DOE shortlisting announced on 18 August 2026, the Company has no agreement, commitment, contract, grant, offtake or funding arrangement with any United States government agency or department, and no such arrangement is proposed as at the date of the announcement. There is no certainty that the meetings will result in any agreement, funding, offtake or transaction.
Next Steps
Completion of these work streams is subject to the availability of equipment, personnel, laboratory capacity, funding and regulatory approvals, and to completion of the Proposed Transaction. Timing is indicative only.
The Position
Within three days of the DOE shortlisting, AT4 has material on the ground at Del Sol, trials running on both metals, engineering proposals in hand and two permit applications in progress. The sequence is coherent: concentrate the feed, produce the empirical dataset, engineer and cost the circuits, then take that package to the federal funding programs.
This article is general information only. It is not financial product advice and does not take into account any person’s objectives, financial situation or needs. Investors should read the Company’s ASX announcements in full, including those dated 28 July 2026, 19 August 2026 and 21 August 2026, together with the cautionary and forward-looking statements contained in them, and obtain independent advice before making any investment decision.
