Utah's Kennecott Mine will begin recovering tellurium, an extremely rare and valuable byproduct of copper smelting. Photo: Robert Thomas

SALT LAKE CITY, Utah. (AP) — It is eight times rarer than gold, in high demand for its use in photovoltaic solar cells and will soon be recovered in Utah at Rio Tinto’s Kennecott mine as a byproduct of copper smelting.

Tellurium is one of the least common elements on Earth, but the company later this year plans to begin recovery operations, with the capacity to produce 20 tons per year, the Desert News reported.

The recent announcement by Rio Tinto means there will be a new North American supply chain for the critical mineral, which after it is alloyed with other elements such as cadmium, forms a compound with enhanced electrical conductivity.

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The thin films from the compound efficiently convert sunlight into electricity. Tellurium also can be added to steel and copper, making them easier to cut, and is used in the manufacturing of night vision goggles for the military.

“The minerals and metals we produce are essential to accelerate the transition to renewable energy,” said Rio Tinto Kennecott managing director Gaby Poirier. “Adding tellurium to our product portfolio provides customers in North America with a secure and reliable source of tellurium produced at the highest environmental and labor standards with renewable energy.”

Recovery of tellurium will require a $2.9 million investment by the company with the construction of a new plant that is expected to start production late this year.

That new supply chain for tellurium will add to domestic production, which is chiefly carried out at a mining operation in Amarillo, Texas.
Utah Gov. Spencer Cox said this addition to Rio Tinto’s Utah portfolio is welcome news.

“With abundant natural resources, Utah is ideally positioned to help supply the critical minerals essential to maintain American manufacturing competitiveness. Rio Tinto’s smelter at Kennecott is one of only two that is capable of producing copper and other critical minerals,” he said. “The new tellurium plant is another valuable contribution to critical mineral independence and energy security in the United States.”

Michael Moats, professor of metallurgical engineering at the Missouri University of Science and Technology, said boosting the domestic supply of tellurium is critical for the United States in the arena of renewable energy and national defense.
Moats heads up the university’s O’Keefe Institute, which does research dedicated to promoting a sustainable supply of critical minerals for the United States.

He said globally there are roughly 500 tons of tellurium produced each year, so Rio Tinto’s entry into the market is significant.
“Because the tellurium market is so small, 20 tons is quite lot,” he said. “The ability to have 20 tons produced here in America helps our country mitigate those supply concerns.”

The addition of tellurium builds on an already robust and diverse mining landscape in the state.
In Utah, mining is a nearly $4 billion industry, with copper as the most valuable commodity. In its 118 years of operation, Kennecott — one of the largest man-made open pit excavations in the world — has delivered more than 20 million tons of refined copper ore and is one of the top-performing mines globally.

A couple of years ago, the hot renewable energy market drove a $1.9 billion investment by Rio Tinto to expand the life of its mine into 2032, with a goal of delivering close to 1 million metric tons of refined copper.

Along with producing nearly 20% of the U.S. supply of copper, Kennecott’s smelting process also recovers gold, silver, platinum, palladium and selenium. Its Copperton concentrator recovers molybdenum, which has one of the highest melting points of all pure elements.

With the addition of tellurium, Rio Tinto is diving into the growing market for solar energy generation, which increased by 22% on a global scale in 2019. About 20% of U.S. electrical generation is from renewable energy, including solar.