Boron, California

Lithium from waste rock

U.S. Borax, part of Rio Tinto, operates California’s largest open pit mine in Boron, California—one of the richest borate deposits on the planet. And, where there is boron, you’re very likely to find lithium.


New process turns waste into lithium

In 2019, an initial small-scale trial successfully proved the process of roasting and leaching waste rock at Boron could recover high grades of lithium. Rio Tinto then created a lithium demonstration plant on site to start producing battery-grade lithium. The demo plant is the next step in scaling up a breakthrough lithium production process (developed at Boron) to recover the critical mineral and extract additional value out of waste piles from more than 90 years of mining at the operation.

The lithium plant has a design capacity of 10 tonnes per year of battery-grade lithium. It ran throughout 2021 to optimize the process and inform Rio Tinto’s feasibility assessment for progressing to a production scale plant with an initial capacity of at least 5,000 tonnes per year, or enough to make batteries for approximately 70,000 electric vehicles.

A critical mineral hiding in the desert

A critical mineral hiding in the desert

The challenge was clear: What can we extract from our waste streams at Boron?

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Environmental sustainability

At our current industrial-scale operations in Boron, California, we continually look for ways to reduce water and energy use and greenhouse gas emissions. We have been repeatedly honored with Solid Waste Reduction Awards from the California Integrated Waste Management Board.

Learn more about our sustainability initiatives  ›

U.S. Borax becomes first open pit mine to transition to renewable diesel

Making history

U.S. Borax becomes the world's first open pit mine to transition to renewable diesel.

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A critical mineral hiding in the desert

Managing waste

Our lithium plant at Boron Operations will be a zero solids waste plant.

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Partnering for success

Development of this project at Boron draws on Rio Tinto’s long standing partnership with the U.S. Department of Energy’s Critical Materials Institute (CMI), which is focused on discovering ways to economically recover critical mineral by-products from existing refining and smelting processes. CMI experts worked alongside Rio Tinto technical leads to help solve a number of key processing challenges to produce battery grade lithium at Boron.

Giving back to our communities is a hallmark of business for Rio Tinto. The Borax Visitor Center Foundation—made up of company and community leaders—oversees the disbursement of Visitor Center funds through an annual grant program. The grants support nonprofit, tax-exempt, and governmental organizations in and around Boron. Founded in 1998, the foundation has returned more than $300,000, including $100,000 in scholarships, to the community over the past two decades.

Boron in the news

Boron might still look like a 19th-century mining town, but its potential as an energy producer is distinctly 21st century
The Kern County NBC affiliate, KGET, runs a story on U.S. Borax's 150th birthday and how Rio Tinto discovered a quantity of lithium—a mineral essent... Read More
Lithium: A Sustainable Source in the Desert
A breakthrough method for extracting lithium from waste rock at our Boron, California mine presents exciting opportunities for producing battery-grade lithium... Learn More
Rio Tinto achieves battery grade lithium production at Boron plant
Rio Tinto has commenced production of battery-grade lithium from waste rock at a lithium demonstration plant at the Boron mine site in California, United States. Read More