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U.S. Army opens future domestic source of antimony sulfide

By Daniel Flynn September 22, 2025

STIBNITE, ID -- The U.S. Army's Joint Program Executive Office Armaments and Ammunition (JPEO A&A) joined Perpetua Resources Inc. to kick off the Stibnite Gold Project in central Idaho. The project seeks to redevelop an abandoned mine site in Stibnite for gold and other materials. One of the key materials resulting from the gold mining operation is antimony sulfide, a critical component used in ammunition production. The U.S. previously obtained antimony sulfide from foreign sources until 2021 when that supply ended.

The kickoff event recognized key permitting milestones and the start of planning for construction activities and was hosted by Jon Cherry, president and chief executive officer of Perpetua. Maj. Gen. John T. Reim, Joint Program Executive Officer Armaments & Ammunition and Picatinny Arsenal Commanding General, joined Idaho Governor Brad Little and Deputy Under Secretary of Agriculture for Natural Resources and Environment Kristin Sleeper, as well as other key project stakeholders at the event.

"The Stibnite project currently holds the largest identified reserve of antimony in the U.S. At an estimated 148 million lbs., it is one of the largest antimony reserves outside of foreign control" said Reim. "This mine represents the nearest-term solution for a secure, reliable, domestic resource for military grade antimony sulfide. And it is in keeping with the Army's ongoing 'Ground-to-Round' assured munitions strategy to locate and engage with domestic sources for critical materials as we modernize and fortify the Arsenal of Democracy."

The event highlighted the important role Picatinny Arsenal has played in the Army's push to establish a complete domestic supply chain, from raw material access to material processing to ammunition production.

"The support of numerous organizations at Picatinny have been crucial to advancing this strategy and addressing a critical supply chain issue for the Defense Department," said Reim.

The JPEO A&A and the Office of the Project Manager for Maneuver Ammunition Systems (PM MAS) initiated a $22.4M Defense Ordnance Technology Consortium effort in 2023 to develop a process for producing military grade antimony sulfide from raw ore. The effort has already completed lab-scale testing and is in the process of completing a pilot-scale operation. In support of the project, U.S. Army Combat Capabilities Development Command (DEVCOM) Armaments Center is providing technical support and Army Contracting Command - New Jersey is providing contracting support. Due to the contributions from these groups at Picatinny, the process for refining antimony, a key step in the supply chain for ammunition, is expected to be available by 2026.

Further, JPEO A&A, PM MAS, and DEVCOM provided subject matter expertise to the Defense Production Act Investments (DPA) Program for a $59.3M project with Perpetua to complete environmental and engineering studies necessary to complete environmental permitting requirements.

In January 2025, Perpetua was issued a Final Record of Decision (ROD) from the U.S. Forestry Service, a crucial National Environmental Policy Act permitting milestone. The Final ROD allowed Perpetua to focus on advancing the Project towards a construction decision, including finalizing the remaining federal and state permits and securing financing. The issuance also allowed Perpetua to maintain their planned schedule for operations and production of raw antimony sulfide to begin in late-2028. In addition, just before the ceremony Perpetua was issued their Notice to Proceed meaning all federal and state permits are in order. Once financial assurance is received, Perpetua will be able to break ground.

This mine contains the raw antimony sulfide ore that can be extracted and refined into military grade antimony sulfide, which is a key ingredient in nearly 30 percent of all military ammunition items, mainly in primers, which initiate the combustion of the propellant that generates the gas pressure needed to launch a projectile. The high-quality raw antimony sulfide at the mine will enable further refinement to the military grade necessary to ensure primers operate reliably in all operating environments. In addition, there is a substantial commercial market for antimony. It is used as a fire retardant in safety equipment, automotive braking systems, and household goods such as mattresses and fabrics used in children's clothing. It can also be found in lead-acid batteries, anti-friction bearings, rubber, ceramics, glass, and pharmaceuticals.

Since 2010, Perpetua has been working closely with the U.S. Department of Agriculture and its agency the U.S. Forestry Service to restart the mine in Idaho through the Stibnite Gold Project to provide a sustainable solution by restarting domestic antimony sulfide production. This included remediation for previous water contamination and ensuring the new project meets all environmental regulations for permitting. Perpetua engaged frequently with the Forestry Service during the DPA project. The close communication was important to meet key permitting timelines, to submit sufficient documentation and information, and to address comments during the process leading to successful issuance of the Final ROD.