Why clay holds lithium at all
Lithium turns up in 3 places, dissolved in salty water called brine, locked in a hard rock called pegmatite, and, geologists now say, packed into ordinary looking clay. For decades nobody built a mine around the third kind. The United States Geological Survey explains why. A caldera, the crater left after a supervolcano collapses, can trap lithium rich magma fluid instead of losing it, if the caldera stays a closed system with nowhere for that fluid to drain. That trapped fluid concentrates lithium into a claystone rich in a clay mineral called hectorite. At the McDermitt caldera on the border of Nevada and Oregon, about 45 kilometers long, 35 kilometers wide, and formed about 19 million years ago, a separate study found a similar lithium rich fluid turned another clay mineral, smectite, into a denser one called illite.
Nevada counts more of it in clay
The Nevada Division of Minerals, the state government regulator, counted the difference in a presentation given in January 2025. A reserve is the part of a discovery a company has proven it can mine and sell at a profit right now. A resource counts everything found so far, proven or not, including rock that may never become a mine. Across clay and sediment lithium projects in Nevada, the division counts a 4.28 million ton reserve and 117 million tons of resources. Across brine projects in the state, it counts only 0.36 million tons of reserves and 1.52 million tons of resources.
A reserve is the part of a discovery proven profitable to mine right now. A resource counts everything found so far, including rock that may never become a mine. Nevada counts about 12 times more reserve tonnage in clay than in brine, and an even wider gap in total resources. All 4 figures are the state minerals division own count.
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| Clay, reserves | 4.28 |
| Brine, reserves | 0.36 |
| Clay, resources | 117 |
| Brine, resources | 1.52 |
The biggest reserves are not where the mining is
The same pattern holds project by project. Thacker Pass, a clay deposit, carries a 14.3 million ton reserve. Rhyolite Ridge, also clay, carries 3.4 million tons. Clayton Valley, also clay, carries 1.76 million tons. Silver Peak, the only lithium mine running in Nevada today, is a brine operation, and carries the smallest reserve of the 4, just 0.36 million tons.
All 4 figures are reserve totals from the state minerals division, as of the date closest to the presentation for each named project.
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| Thacker Pass, clay | 14.3 |
| Rhyolite Ridge, clay | 3.4 |
| Clayton Valley, clay | 1.76 |
| Silver Peak, brine | 0.36 |
Washington is already paying for the plants clay needs
Clay needs a processing plant that brine never did, and Washington has already paid toward building 3 of them. The Department of Energy backs Lithium Americas at Thacker Pass with a 2.26 billion dollar loan, Ioneer at Rhyolite Ridge with a 996 million dollar loan, and American Battery Technology Company with a 144 million dollar grant toward a recycling facility, not the Tonopah Flats mine directly. Together the 3 figures put more than 3.4 billion dollars in federal loans and grants behind clay focused companies in Nevada.
The American Battery Technology Company figure funds a recycling facility, not the Tonopah Flats mine directly. Together the 3 figures total 3.4 billion dollars, a sum calculated from the state minerals division separate figures for each company.
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| Lithium Americas, Thacker Pass, a loan | 2,260 |
| Ioneer, Rhyolite Ridge, a loan | 996 |
| American Battery Technology Company, a grant for recycling | 144 |
One deposit, counted twice, 3 years apart
The claystone deposit American Battery Technology Company holds at Tonopah Flats shows how fast the count can grow. In 2023 the company reported an early, unproven inferred resource of 15.8 million tons of lithium carbonate equivalent, a way to compare different lithium compounds. Chief Executive Officer Ryan Melsert said this at the time.
Having identified one of the largest premier lithium deposits in the U.S. is extremely exciting.
Ryan Melsert, Chief Executive Officer of American Battery Technology Company. Source 4.
By 2025 the company reported a 21.15 million ton resource in a different compound, lithium hydroxide monohydrate, plus a 2.73 million ton proven and probable reserve and a claystone grade of 755 parts per million lithium, well above the 300 parts per million cutoff used to define ore. It now plans 30,000 tonnes a year of battery grade lithium hydroxide for 69 years.
The clay did not change. What changed is that companies worked out how to measure it, and how to process it.