Perpetua Resources signs antimony testing agreement

Catie Clark//May 12, 2021

Perpetua Resources signs antimony testing agreement

Catie Clark//May 12, 2021

A stibnite specimen on display at the New York Museum of Natural History.
A stibnite specimen on display at the New York Museum of Natural History. Public Domain via Wikimedia Commons

Antimony’s current use in batteries is so important that the future of electric vehicles may depend on it. It is also an essential metal for making alloys. It’s a no-brainer that antimony is on the U.S. list of 35 critical mineral commodities of strategic importance. That’s why the just-signed agreement between Perpetua Resources and U.S. Antimony is a big deal.

Perpetua announced the agreement on May 3 to have U.S. Antimony test Perpetua’s antimony concentrates at its facilities. U.S. Antimony owns the only antimony smelter in the U.S., located in Montana. U.S. Antimony entered into an agreement in January with battery-producer Ambri to supply antimony. Though Perpetua’s Stibnite property is not yet in production, the Ambri and U.S. Antimony agreements underscore the viability of the bringing the previously-abandoned Stibnite mine back into production.

The last time antimony was produced in the United States from domestic ores was 20 years ago. Most of the nation’s supply is imported from. China holds an estimated 60% of the world’s antimony resources.  The U.S. has just 3%. Productions estimates from Perpetua indicate that the Stibnite mine could supply up to 35% of domestic demand in the first six years of operations.

Perpetua intends to mine Stibnite  for both gold and antimony. The deposits is one of the largest known economic deposits of antinomy outside of China. Historically, the property produced gold and silver during the 1930s. It also produced tungsten and antimony during World War II for the war effort. From 1941 to 1945, Stibnite mined more tungsten and antimony than any other mine in the country, producing 40% of the nation’s domestic supply of tungsten and 90% of its antimony. The United States Geological Survey considered the tungsten mineralization to be exhausted by the WWII mining efforts.

Stibnite is named for the mineral form of antimony trioxide, which forms stunning steel-grey elongated prisms that are often iridescent. Most of the antimony at Stibnite is stibnite, with very minor amounts of oxidized antimony minerals.

Perpetua Resources is headquartered in Boise and is in the process of permitting the Stibnite site to mine gold and antimony.  The company is conducting voluntary clean-up activities at Stibnite, mainly to divert surface waters away from tailings during its first phase.

U.S. Antimony is headquartered in Thompson Falls, Montana, which is also the location of its smelter. Most of the antimony concentrates processed in Thompson Falls are currently from Canada. The company also owns owns and operates precious metal and antimony mines and a smelter in Mexico. In addition, U.S. Antimony also owns and operates the Bear River Zeolite Corp. in southeast Idaho, which mines a low-clay zeolite deposit outside of Preston.

Ambri Corp. is a privately-held manufacturer of molten salt and liquid metal batteries used mostly for energy storage for solar and wind power generation. Bill Gates is one of its investors.