American Tungsten & Antimony (ASX:AT4) progresses Del Sol refinery development pathway with tungsten and antimony trials underway
American Tungsten & Antimony is progressing operational programs at the Del Sol hydrometallurgical refinery in Amargosa Valley, Nevada, with wet table trials underway on tungsten and antimony mineralisation as the Company advances work to establish the front end concentration steps required to expand Del Sol into proposed APT processing capability and optimise antimony concentration ahead of a restart trial of the refinery’s existing alkaline leach and electrowinning circuit.
Highlights
Wet table trials have commenced at Del Sol on scheelite bearing tungsten mineralisation sourced from AT4’s Dutch Mountain Tungsten Project and third party material sourced near Del Sol, as the next step towards expanding Del Sol into APT processing capability.
Engineering proposals have been received from shortlisted firms for the proposed APT expansion, with engagement of the preferred engineering firm targeted within the next 2 weeks.
Approximately 3 tonnes of stibnite bearing mineralisation has been hauled from White Spar to Del Sol for wet table trial work, alongside samples and drill core from Antimony Canyon.
AT4 was shortlisted by the US Department of Energy on 18 August 2026 for commencement of negotiations regarding the scope and terms of a potential financial award of up to US$18 million under a US$162 million initiative supporting critical minerals recovery from domestic industrial sources.
The work programs underway at Del Sol are directed at establishing the front end concentration step required to expand the refinery into APT production and optimising the concentration of antimony mineralisation ahead of a full restart trial of the existing alkaline leach and electrowinning circuit.
AT4 Chief Executive Officer Casper Adson said,
“AT4 is entering into 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.”
For tungsten, AT4 is conducting wet table trials using scheelite mineralisation from its Dutch Mountain Tungsten Project in Utah, together with external third party tungsten sources located near Del Sol in the southwestern United States.
The wet table program allows various sources of feed to be tested across a range of crush and grind sizes to determine the ability to produce a scheelite concentrate through gravity separation methods.
The program is assessing concentrate grade and upgrade ratio, recovery and loss deportment, liberation and sizing, feed variability response and production of concentrate for downstream testwork.
The proposed APT expansion is progressing through an engineering review process, with AT4 having issued requests for proposal to 5 international engineering firms covering the proposed APT circuit, expansion of antimony flake capacity and additional specialty antimony product circuits, with several proposals now received.
The appointed engineering firm will be scoped to deliver a design basis and capital and operating cost estimate for a domestic US APT refinery at Del Sol.
Alongside the tungsten workstream, AT4 is progressing antimony concentration trials using material from White Spar and Antimony Canyon.
Approximately 3 tonnes of stibnite bearing mineralisation has been extracted from the existing small scale extraction zone at the White Spar Antimony Mine in Yavapai County, Arizona, and hauled to the Del Sol Refinery for wet table trials.
Samples and drill core from Antimony Canyon are also being processed through the wet tables to confirm that Antimony Canyon material is metallurgically compatible with the Del Sol flowsheet and establish the concentration response ahead of any future development decision.
The concentration trials are the immediate precursor to a full restart trial of the Del Sol antimony flake circuit, which AT4 is targeting 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.
The results are intended to be used in capacity expansion engineering, specialty product development programs covering Regulus II antimony metal ingot, antimony trisulphide and sodium antimonate, commercial discussions with prospective offtake counterparties and applications under US federal programs supporting domestic critical minerals capability.
AT4 Chief Executive Officer Casper Adson, together with the Nexus Metals team, will undertake meetings in Washington D.C. and New York with potential strategic stakeholders.
The aim of the meetings is to introduce Del Sol as a constructed and permitted domestic refining asset and progress development activities for APT and antimony refining at the facility.
The Company noted that, beyond the DOE shortlist announced on 18 August 2026 to commence negotiations regarding potential funding, AT4 had no agreement, commitment, contract, grant, offtake or funding arrangement with any US government agency or department as at the date of the announcement.
AT4’s next steps include completing wet table trial programs on tungsten and antimony mineralisation, appointing the preferred APT engineering firm, conducting laboratory scale APT testwork, commencing the Del Sol antimony flake circuit restart trial, progressing permitting applications and completing the Proposed Transaction.
Completion of these work streams is subject to the availability of equipment, personnel, laboratory capacity, funding and regulatory approvals, as well as completion of the Proposed Transaction.