The US Department of Defense (DoD) has awarded Perpetua Resources US$200,000 of funding to evaluate producing military-grade antimony trisulphide from its Stibnite Gold project in Idaho.

The study will test if samples from Stibnite Gold can successfully be processed to meet military-grade specifications, with a second study to evaluate using antimony metal as a feed. On successful findings, further funding could be made available for developing pilot operations.

This would not be the first supply of antimony trisulphide in the USA. United States Antimony Corporation (USAC) has produced over 15t of antimony contained in antimony trisulphide in 2022 so far from its Thompson Falls plant in Montana. The plant processes ores and concentrates from USAC’s antimony mines in Mexico, with a focus on producing antimony trioxide (ATO).

Antimony demand is mainly driven by lead-acid batteries (largely sourced from recycled sources) and flame retardants (the main ATO market and now the main driver of primary mine supply). While the combined outlook in these sectors is modest at best, antimony remains high on the list of critical materials, especially given its use in military equipment. Project Blue’s Critical Materials Risk Index (CMRI) ranks antimony as #9/40 with a high supply risk securing its top-10 position. China’s hold on antimony mine supply has dwindled and it is now critically reliant on importing significant volumes of concentrate to meet its domestic ingot and ATO industry – currently in short supply.

China remains the largest source of sellable ingot (ingot not consumed captively to ATO) but supply from Vietnam and Tajikistan has ramped up to offer alternative sources, which could form part of the second alternative feedstock study by Perpetua. With Vietnam’s output nearly exclusively based on Russian feed, establishing a sustainable supply chain remains challenging and the only other plant of significant scale in Oman is competing for feed against Chinese producers. USA’s antimony ingot industry effectively vanished in the early 2000s, with USAC’s Thompson Falls the last one standing but producing only small volumes. As with other critical materials, the USA is targeting establishing secure supply chains for military uses.