American Tungsten Starts Del Sol Antimony Refinery Ahead of Schedule
Key Takeaways
- AT4 has commenced the Del Sol Hydromet Refinery restart ahead of schedule, processing White Spar Antimony Mine material through the leach and electrowinning circuit at its Amargosa Valley, Nevada facility.
- The campaign is the first physical demonstration of AT4's US mine-to-metal strategy, producing domestically refined antimony flake and Regulus II ingot without requiring new infrastructure or additional permitting.
- Executive Order 14415, signed 20 July 2026, mandates domestic or allied sourcing of critical materials across US defence supply chains — antimony is explicitly central to those requirements, and physical product samples are a prerequisite for defence qualification discussions.
- AT4's US subsidiary has been selected by the Department of Energy to enter award negotiations under the ASCEND-Sb programme, representing a potential funding award of up to US$18 million, though no commitment has been made.
- The acquisition of both the Del Sol Refinery and White Spar Mine from Nexus Metals remains conditional on shareholder approval at a general meeting scheduled for 21 September 2026 — the restart is proceeding under pre-completion arrangements, and there is no certainty the acquisition will complete.
Del Sol refinery restart commences ahead of schedule
American Tungsten & Antimony Ltd (ASX: AT4; OTCQB: ATALF) has commenced a restart campaign for the leach and electrowinning circuit at the Del Sol Hydromet Refinery in Amargosa Valley, Nevada, ahead of schedule, processing material from the White Spar Antimony Mine in Yavapai County, Arizona. The campaign represents the first physical demonstration of AT4’s US mine-to-metal strategy, converting domestically sourced mineralisation into refined antimony product at a permitted US facility.
The restart has been fast-tracked specifically to demonstrate US domestic antimony processing capability for defence and government needs. Independent process engineering specialists, working alongside AT4’s technical experts and the site operating crew, are supervising the campaign.
It is important to note that AT4 currently holds no legal or beneficial interest in the Del Sol Refinery or the White Spar Antimony Mine. The restart is being undertaken in cooperation with Nexus Metals under pre-completion arrangements that permit AT4 to progress agreed work programmes at the assets prior to finalising the acquisition. That acquisition remains conditional, including on shareholder approval at a general meeting scheduled for 21 September 2026. There is no certainty the acquisition will complete.
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What’s happening inside the restart campaign
From mine feed to antimony flake
White Spar mineralisation, recovered from the mine’s existing small-scale extraction zone, as well as material upgraded in a gravity beneficiation circuit, is being processed through the Del Sol hydrometallurgical circuit. Antimony metal flake produced during the campaign will be collected, washed, dried, weighed, and assayed, with third-party umpire laboratory verification performed on keepsake samples.
A comprehensive sampling and assay protocol covers head samples, intermediate samples, tailings, and final product. Critically, the campaign operates within the facility’s existing permitted feed envelope, meaning no new infrastructure or additional permitting is required.
Objectives the campaign is designed to deliver
The restart campaign has been designed to pursue the following objectives:
- Produce antimony flake for product qualification, sampling, and technical discussions with prospective offtakers, strategic partners, and US government agencies
- Produce Regulus II antimony ingot through remelting of Company-produced flake, together with fire refining test work to assess achievable product quality
- Verify process parameters, reagent consumption, antimony recovery, and achievable antimony flake grade on White Spar feed material
- Generate feedstock for planned test work on specialty antimony products, such as antimony trisulphide
- Advance the technical basis for applications under US Federal programmes supporting domestic critical minerals processing
A second, larger campaign is proposed to build on these results and generate engineering data required to support scoping study cost estimates for expanding Del Sol’s antimony capacity.
Casper Adson, Chief Executive Officer
“Commencing the restart campaign at the Del Sol refinery is a critical milestone for the Company. AT4 has fast-tracked the restart to demonstrate the capability of the Del Sol circuit using US-sourced material. An existing, permitted facility enables the circuit to be restarted without the need to add new infrastructure or lengthy permitting delays.”
Why antimony and why now — the US supply chain imperative
Antimony is a critical metal with a surprisingly wide range of defence and industrial applications. Antimony trisulphide is an essential component of primer compositions for small arms and medium calibre ammunition. Beyond that, antimony is used as a hardening agent in projectiles, in military-grade lead-acid batteries, in flame retardant systems, and in night vision and infrared guidance systems. It is also emerging as a critical raw material for the US semiconductor and advanced electronics sectors.
The problem is where the US currently gets it. The country remains overwhelmingly import-dependent for antimony supply, with China the dominant global supplier. That dependence has become increasingly untenable from a national security standpoint.
Executive Order 14415, “Securing America’s Defense Supply Chains and Ensuring Domestic Acquisition of Critical Materials,” signed on 20 July 2026, makes the policy direction explicit. The Order states that not only finished military equipment, but also the critical materials and components needed to manufacture, maintain, and repair that equipment, must be sourced domestically or from allied nations. It directs defence contractors to trace supply chains back to the origin of raw materials and to qualify alternative domestic or allied sources where they rely on unreliable foreign suppliers.
This is where AT4’s position becomes material. Product qualification, a key requirement in defence and industrial supply arrangements, cannot begin without physical samples. Presenting domestically refined antimony produced from US material at a permitted US facility is fundamentally different from presenting a development plan.
Timothy Morrison, Executive Chairman
“US policy increasingly requires domestic and allied supply of critical materials used in defense supply chains, and antimony sits at the centre of these requirements. The ability to demonstrate physical production from US material differentiates AT4 from projects that remain at the development stage…”
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Government engagement and the path ahead
AT4’s engagement with US government agencies is advancing in parallel with the physical restart work. AT4’s wholly owned US subsidiary was selected by the US Department of Energy (DoE) to enter award negotiations under the Mines & Metals Capacity Expansion programme in respect of the ASCEND-Sb Project, representing a potential award of up to US$18 million (refer ASX announcement 19 August 2026). It must be noted that selection to enter negotiations does not constitute a funding commitment, and discussions with the DoE regarding that funding package are ongoing.
The Company is also progressing existing applications with other agencies and initiating new applications following a programme of meetings recently completed in Washington, D.C.
On the tungsten side, test work is continuing at Del Sol on material from Dutch Mountain, Tennessee Mountain, and third-party sources, assessing upgrading of scheelite and informing flowsheet selection for the proposed ammonium paratungstate (APT) circuit at Del Sol. APT is the principal traded tungsten intermediate. AT4 has engaged Metso to complete a scoping study for the proposed APT circuit at Del Sol (refer ASX announcement 1 September 2026).
Near-term next steps include:
- Funding and offtake discussions for production of antimony from US sources on US soil
- An extended campaign to collect operating data for the refinery antimony expansion study
- Test work on specialty antimony products, including antimony trisulphide, using Company-produced flake
- Completion of the Metso APT tungsten scoping study for the proposed expansion of Del Sol into tungsten production
| Activity | Location | Status | Key Milestone |
|---|---|---|---|
| Del Sol antimony restart | Amargosa Valley, Nevada | Commenced (ahead of schedule) | Produce qualification flake & Regulus II ingot |
| ASCEND-Sb / DoE negotiations | USA | Ongoing | Potential award of up to US$18M (not a funding commitment) |
| Specialty antimony product test work | Del Sol, Nevada | Planned | Use Company-produced flake |
| APT tungsten scoping study (Metso) | Del Sol, Nevada | In progress | Scoping study completion |
The restart campaign places AT4 at an early but tangible point on the path from development-stage aspiration to physical product. With Executive Order 14415 tightening the policy environment and defence qualification discussions requiring actual samples, the timing of an ahead-of-schedule restart carries real strategic weight, provided the conditional acquisition completes as planned.
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