A renewed geological assessment of the ancient McDermitt Caldera on the Oregon-Nevada border has confirmed the site holds what could be the largest known lithium deposit in the United States—potentially worth up to $1.5 trillion.
Although the caldera’s lithium-rich clays have been known for years, recent evaluations suggest the scale of the deposit is far greater than previously understood.
Experts say the find could help transform the US into a major player in the global battery supply chain.
The McDermitt Caldera was formed by a supervolcanic eruption 16.4 million years ago. The volcanic activity created a unique geological environment that concentrated vast amounts of lithium in claystone, particularly within lakebed sediments.
At the southern end of the caldera in Nevada, Lithium Americas is advancing the Thacker Pass project—set to begin extraction in 2026 with more than $2 billion in government loans and major investments from companies like General Motors.
On the Oregon side, Australia-based Jindalee Resources is exploring a similarly vast deposit, though no mine has yet been proposed. Officials and geologists suggest it could surpass other domestic sources in scale.
“This feature is 16 million years old, and we’re making decisions in a matter of years,” said Sammy Castonguay, a geologist at Treasure Valley Community College. “We need to understand what’s at stake.”
Estimates suggest McDermitt Caldera could contain between 20 and 40 million metric tonnes of lithium—far surpassing the major reserves found in Bolivia and Argentina. This figure is significantly higher than the previously reported 18 million metric tonnes.
With global lithium demand expected to rise 40-fold by 2040, according to the International Energy Agency, the McDermitt site is being seen as a potential game-changer.
However, extracting lithium from claystone poses technical and environmental challenges. Unlike salt brine operations, the lithium here is embedded in illite, requiring new chemical leaching technologies. Researchers are working on closed-loop systems to minimise water usage and reduce environmental harm.
Local communities remain divided. Malheur County, Oregon’s poorest, could benefit from jobs and infrastructure. But past mining in the region left toxic scars—visible in abandoned mercury waste piles.
Meanwhile, Indigenous tribes and environmental groups have raised concerns about Thacker Pass’s impact on sacred land, water resources, and wildlife habitats.
“The US can’t afford to repeat past mistakes,” said Greg Smith, director of economic development in Malheur County. “We need to do this the Oregon way—with full accountability and shared benefits.”
As the US moves to strengthen its domestic lithium supply under the Inflation Reduction Act and reduce reliance on foreign sources, the McDermitt Caldera is drawing national and global attention. The question now is how, and if, the country will responsibly unlock its vast potential.
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