Del Sol refinery permitted for 100,000 short tons feed capacity expansion

Del Sol Refinery Positioned for Modular Expansion

American Tungsten & Antimony Limited (ASX:AT4) is advancing plans to ramp up and expand the Del Sol Refinery in Nevada, pending completion of its acquisition announced in late July. CEO Casper Adson recently visited the site to assess the plant’s condition and potential for growth. The refinery, already permitted to process 18,500 short tons of feed annually, sits on approximately 40 acres of privately owned land with about 10 acres cleared and fenced for development.

AT4 describes Del Sol as a modular platform primed for capacity increases mainly through equipment additions within the existing footprint. The processing building retains unused floor space suitable for installing additional leach tanks, filter presses, and electrowinning cells. While no formal engineering or feasibility studies have yet been completed, the company sees potential to boost throughput without new construction. The facility benefits from grid power supplied by Valley Electric and adjacency to a utility-scale solar farm, factors that could influence operating costs for the energy-intensive hydrometallurgical process.

Restart and Data Capture to Inform Expansion

Assuming the acquisition closes, AT4 intends to restart the antimony flake circuit in the September quarter of 2026. The restart will be phased, starting with small batches to validate circuit performance before ramping throughput. This cautious approach aims to identify bottlenecks and equipment needs, reducing risks associated with scaling up.

Crucially, the company plans to collect detailed operating data on throughput, recovery rates, reagent use, power consumption, product quality, and labour demands. This dataset will underpin forthcoming engineering studies and support applications for US government funding programs, including the Defense Logistics Agency stockpile initiatives and Defense Production Act Title III funding. However, AT4 cautions that no funding has been secured and eligibility remains uncertain.

Engineering RFPs Target New Products and Capacity

Parallel to the restart, AT4 has issued Requests For Proposal to international engineering firms for a scoping study covering expansion of antimony flake capacity and the addition of new processing circuits. These include Regulus II antimony metal, antimony trisulphide, sodium antimonate, and ammonium paratungstate (APT), a tungsten compound. The company expects that operating data from the restarted plant will allow engineers to tailor designs to the existing infrastructure and improve cost accuracy. No capital or operating cost estimates have been released yet.

White Spar Mine Exploration and Bulk Sampling

In Arizona, AT4’s CEO and geologist recently inspected the White Spar Antimony Mine, which hosts established mining infrastructure but has no JORC-compliant resource or reserve estimates. Historically mined for antimony-silver mineralisation, the site supports AT4’s vertically integrated strategy linking mine to refinery.

The company plans an exploration program involving drone surveys, geological mapping, grab sampling, and a maiden drill campaign, subject to approvals and funding. A bulk sample extraction is also planned to test metallurgical performance through the Del Sol flowsheet at scale. These steps aim to validate White Spar as a reliable feedstock source for the refinery.

Regulatory Engagement on Capacity Expansion

AT4 held a pre-application meeting with the Nevada Division of Environmental Protection (NDEP) to discuss expanding Del Sol’s permitted processing capacity from 18,500 to approximately 100,000 short tons per year. The meeting also covered adding APT production and other critical mineral circuits. The company intends to submit a formal application but emphasises there is no guarantee of approval or timing.

Permitting for tungsten refining will follow a separate pathway, to be progressed alongside the engineering studies. The company notes that permitted throughput limits are regulatory caps, not production forecasts or financial guidance.