Antimony is on the front lines of USA congressional efforts to secure strategic reserves for minerals critical to the defence-industrial supply chain.

The House Armed Services Committee addressed China’s grip on the antimony supply chain in draft legislation, which included a report requiring the manager of the defense stockpile to brief the committee on the status of antimony. The proposed legislation would also require the submission of a five-year outlook for all strategic minerals including current a future supply chain vulnerabilities. Recent geopolitical dynamics with Russia and China have raised concerns around how supply chain disruptions might accelerate, both for antimony and more generally.

Antimony is designated as a critical mineral by the USGS and is used primarily in lead-acid batteries and flame retardants. However, the mineral’s use in armour-piercing bullets, explosives and nuclear weapons means it is critical to the US defence-industrial supply chain.  The USA is largely reliant on importing antimony to meet domestic demand and the majority of its antimony ingot imports come from China. Up until the early 2000s, the USA produced significant volumes of refined antimony ingot and antimony trioxide for domestic consumption. In 2000, five smelters were in operation, however, by 2005 only one operation remained: the Thompson Falls Plant in Montana.

The Thompson Falls plant is built around a zeolite deposit and includes precious metal refining, but its largest revenue stream comes from its antimony smelter with the capacity to produce 6,800tpy of antimony oxide or 2,250tpy of antimony metal. The plant is reliant on imported feedstock, largely integrated with antimony-gold-silver mines in Mexico, all under the ownership of the United States Antimony Corporation (USAC). Ingot production is thought to be minimal at the plant, with much of the reported refined output sold as antimony trioxide for domestic consumption in the USA.

The strategic stockpile of critical materials is managed by the Defense Logistics Agency and is funded by the Treasury Department. After recent sell-offs of the strategic stockpile, which included reductions in titanium, tungsten, tantalum, cobalt and aluminium reserves, the Defense Department recently requested an additional USD$253.5M to procure additional minerals.