Rio Tinto starts producing lithium from waste rock at California mine

Rio Tinto Plc said on Wednesday it has begun producing lithium, the ultralight metal used to make electric vehicle batteries, from waste rock at a borates mine it controls in California.

A demonstration plant has begun operations with annual production capacity of 10 tonnes of the white metal, the Anglo-Australian company said in a press release.

That demonstration plant will run for the rest of the year as Rio decides whether to spend $50 million to build a full-scale production plant with annual capacity of 5,000 tonnes.

Rio has produced borates - a group of minerals used to make soaps, cosmetics and other consumer goods - for nearly a century in the Mojave Desert, about 120 miles (195 km) north of Los Angeles.

That has left behind more than 90 years' worth of waste rock, known in the industry as tailings. Rio said in late 2019 that it had begun probing the tailings for gold and discovered lithium at a concentration higher than rival US projects under development, although the company declined to give the exact percentage.

While the move would mark Rio's first jump into commercial scale production of lithium, several rivals are planning projects that vastly exceed Rio's plans for California.

Lithium Americas Corp, for instance, received final federal approval in January for a Nevada lithium mine that will produce 20,000 tonnes annually once operational in 2023.

Rio also controls Utah's Kennecott copper mine and a lithium deposit in Serbia that has yet to be developed.