USAC receives federal grant

The United States Antimony Corporation (USAC) in Thompson Falls has received a grant from the Defense Logistics Agency (DLA) of the Department of Defense (DOD) in the amount of $510,528 to develop a new domestic source of antimony trisulfide as an alternative to the majority historically supplied by the People’s Republic of China.

USAC began processing six batches (just over 1,102 pounds per batch) of antimony trisulfide on September 13 and will continue the project until September, 2020. The sample batches will be tested for quality assurance and shipped from Montana to Perkins Rouge and Paint, in Milford, Connecticut, to be ground, sized, packaged and quality controlled, according to John Lawrence, CEO of USAC.

“This award to USAC is being issued to establish a firm fixed price contract,” Lawrence commented. “The purpose of this research and development acquisition is to qualify MIL-A-159D antimony trisulfide from sources in North America for the DLA Strategic Materials, National Defense Stockpile.”

Antimony trisulfide is a major component of primers for all center-fired artillery and is a naturally occurring mineral also known as stibnite.

“USAC mines the mineral at a Mexican mine, concentrates it in a flotation mill in Mexico, and ships a very high grade (60-68%) antimony concentrate to Thompson Falls,” Lawrence said, explaining the process. “Here, the concentrate is melted into blocks under proprietary conditions to change the crystallinity to needles.” This process is called liquidation and highly purifies the antimony trisulfide converting the product into “needle antimony” or “crudum.”

Lawrence shared that once these blocks are received by Perkins Rouge and Paint, a major military and commercial supplier of trisulfide extracted from China, they grind and screen the blocks into a specific small size designated “Class 1, Type 1” used in the manufacturing of primers for all center-fired ordnance.

The needle antimony mixes with and detonates the gun powder in ammunition shells when the primer is fired, resulting in the ammunition firing. “The reliability of the primer is extremely important to prevent misfires or hang fires (a delay in firing),” Lawrence added.

With such applications, quality control measures are also of great importance and must abide by stringent standards. Lawrence shared that Specification MIL-A-159D requires a total antimony minimum of 70.5%, total sulfur minimum of 24.8%, insoluble material maximum of 1%, acidity maximum of 0.01%, lead maximum of 0.15%, iron maximum of 0.5%, free sulfur maximum of 0.2%, arsenic maximum of 0.06% and a moisture maximum of 0.02%.

Having “high lead content in the trisulfide will cause jamming in machine gun applications,” was one example Lawrence shared as being a side effect of having poor composition standards.

The history of antimony in the USAC dates to World War II when the War Department received antimony from the Stibnite Hill Mine (which is now owned by USAC), and Idaho’s Sunshine Mine and Yellow Pine District, according to Lawrence. The demand was greater than what these mines could produce, therefore, the War Department ended up purchasing most of the antimony from Mexican mines — the Wadley, Soyatal and Guadalupe.

Lawrence shared that following the war, 40,000 tons of antimony metal, primarily from the Wadley, was purchased by the U.S. government to create a “strategic stockpile.” This stockpile was depleted by 2003.

For the past 16 years, approximately 92% of the world’s antimony has been supplied by China, who is the main antimony trisulfide supplier. Lawrence stated that “this has placed the United States in a very vulnerable position.”

The three Mexican mines (Wadley, Soyatal and Guadalupe) are now controlled by USAC and two of these are currently active in antimony extraction. “All of that product is brought to Thompson Falls to finish processing and is shipped to domestic and foreign buyers,” stated Lawrence with pride that small-town Thompson Falls is playing a major role in reducing U.S. dependency on a foreign country.