American Tungsten & Antimony (ASX: AT4) has engaged Metso, a specialist in minerals processing and metals refining, to complete a scoping study for an ammonium paratungstate (APT) production circuit at the Del Sol Refinery in Nevada.

The refinery is the subject of the company's conditional acquisition, which was announced in late July 2026.

APT is a vital chemical intermediate used primarily as the main industrial source for producing high-purity tungsten oxides, tungsten metal powder, and tungsten carbide. Tungsten is designated as a critical mineral by the US government, reflecting its importance to national security, defence, and advanced manufacturing, and APT is an intermediate product required for the downstream tungsten supply chain.

Domestic conversion capacity for tungsten concentrate to APT in the US is limited, with China accounting for the large majority of both global tungsten mine production and APT processing capacity. This concentration has driven recent US policy measures aimed at rebuilding domestic critical minerals supply chains, including funding programs such as the Department of Energy's Mines & Metals Capacity Expansion initiative under which AT4 is pursuing award negotiations. The company considers that establishing tungsten conversion capability advances its goal of becoming a vertically integrated supplier of tungsten critical minerals for US defence and industrial needs.

AT4 CEO Casper Adson has commenced a program of meetings in Washington, DC, including at the White House, with US government agencies and key stakeholders. The meetings are intended to initiate new conversations and advance those already underway between AT4 and core stakeholders, with a particular focus on the government agencies with which the company is seeking to partner in relation to grant and funding instruments, both in the near term and over the longer term.

A key focus of this engagement is to continue and expand on the progress made with the US Department of Energy in relation to the ASCEND-Sb Project, for which AT4 was selected to enter award negotiations under the Mines & Metals Capacity Expansion program. The company is concurrently progressing existing applications with other agencies and initiating new applications where opportunities are identified, including in connection with the tungsten APT capability described in this announcement.

"Tungsten is one of the most strategic commodities for the United States. Defence, aerospace and industrial manufacturing are all exposed as its supply is offshore and controlled by adversaries," Mr Adson said.

"Rebuilding the ability to convert tungsten concentrate into tungsten APT on US soil is a question of national interest.

"Del Sol is a constructed and permitted hydrometallurgical plant on American soil. Putting an APT circuit inside an existing footprint rather than building on a greenfield site has the potential to materially reduce the capital required and the timeline to commence producing a domestic tungsten product."

The proposed Phase 1 circuit is to be sized at 2,500 tonnes per annum (tpa) APT, with a potential future Phase 2 expansion proposed for 5,000 tpa APT.

Mr Adson said the capital and operating cost estimates from the study will enable the company to engage US funding programs available for the support of domestic critical minerals sovereignty and independence. Key milestones ahead for investors to monitor include the completion of the Metso scoping study and its cost estimates, finalisation of the conditional Del Sol acquisition, and the outcome of the company's various US government funding applications.

AT4 was steady at 7.3¢ with a market capitalisation of $131.0M prior to markets opening.