Rio Tinto announced that it has started producing tellurium at its Kennecott copper operation near Salt Lake City, UT.

With the start of production, Rio Tinto becomes one of only two U.S. producers of the critical mineral used in advanced thin film photovoltaic solar panels.

The tellurium will be refined in North America by 5N Plus, a leading global producer of specialty semiconductors and performance materials, under a commercial agreement between 5N Plus and Rio Tinto. The refined tellurium will primarily be supplied to First Solar, the only American company among the world’s 10 largest solar manufacturers, under an existing supply contract between 5N Plus and First Solar. 5N Plus will also use the tellurium to manufacture ultra-high purity semiconductor materials at its facility in St. George, UT, to serve the security and medical imaging markets.

Approximately 18 t (20 st) of tellurium will be produced per year through a new $2.9 million circuit built at the Kennecott refinery. This valuable material is recovered from by-product streams generated during the copper refining process, reducing the amount of waste that needs to be treated and discarded as mine tailings.

Tellurium is listed as a critical mineral by the U.S. Government due to its importance to the economy and energy security.

“We are proud to deliver a new domestic supply of tellurium to support the manufacturing of solar panels and other critical equipment here in the United States,” Rio Tinto Copper chief operating officer Clayton Walker said in a statement. “Approximately 90 percent of the world’s tellurium resource is contained in copper ore and no other metal has more critical mineral by-products than copper. The Kennecott team is constantly looking for ways to extract new critical minerals to meet emerging demand for the clean energy transition.”

5N Plus President and chief executive officer Gervais Jacques said, “As a leading global supplier of specialty semiconductor compounds for applications in renewable energy, security and medical imaging, 5N Plus is proud of this partnership with Rio Tinto, and to further leverage its expertise in the transformation of mining and metallurgical by-products into high purity value-added critical minerals such as tellurium, here in North America.”

Tellurium is one of 10 metals and products recovered from ore extracted at Kennecott, which produces nearly 15 percent of U.S. copper with the country’s lowest carbon footprint.