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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsNo confirmed reserve worth $1.5 trillion has been established beneath a U.S. supervolcano. The headline refers to lithium-bearing clay and lake sediments in the ancient McDermitt Caldera, which straddles Nevada and Oregon. The often-repeated $1.5 trillion figure is a rough calculation reported by secondary media—not an official valuation of lithium that can be mined, sold, or turned into profit.
What is the McDermitt Caldera, and where is the lithium?
The McDermitt Caldera is a volcanic depression on the Nevada–Oregon border, formed about 16.4 million years ago during the early stages of Yellowstone hotspot volcanism. The lithium at issue is hosted in ancient lake sediments and clay minerals; it is not a deposit beneath an active volcano. The U.S. Geological Survey (USGS) describes its origin as a geological model in which magmatic fluids accumulated in a closed caldera lake, became concentrated through evaporation, and were captured in clay minerals. USGS’s 2025 synthesis calls the area one of the world’s largest lithium deposits, but that does not establish a global record under a consistent resource definition.
How much lithium is there, and what does “largest” mean?
The figures in circulation describe different things, so they should not be treated as interchangeable.
| Figure or description | What it refers to | What it does not establish |
|---|---|---|
| Approximately 2 million tonnes | USGS’s estimate for what it calls the largest single lithium resource in the United States at McDermitt. USGS project page. | A confirmed global ranking, an economically recoverable reserve, or a $1.5 trillion asset value. |
| 20–40 million metric tons | A range reported by Earth.com on April 21, 2026, in its account of the trillion-dollar claim. | A USGS or Department of Energy (DOE) resource estimate, or proof that this quantity can be mined and sold. |
| 25–150 million metric tonnes | A USGS model of lithium potentially yielded by 100 km³ of resurgent magma, discussed in its 2025 geological synthesis. | A measured deposit quantity, proven reserve, or recoverable mine output. |
| “North America’s largest confirmed lithium resource” | DOE’s description of the Thacker Pass mine site. DOE project overview. | The same geographic scope as the broader McDermitt Caldera estimate or proof of the world’s largest deposit ever. |
These labels answer different questions: a resource estimate describes a geological concentration under a stated assessment, while a reserve refers to material demonstrated to be economically recoverable under particular conditions. The available descriptions also differ in geographic scope: McDermitt is the broader geological region, while Thacker Pass is a specific project within it. Without comparable estimates and definitions, “world’s largest ever” is not a supported conclusion.
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Where did the $1.5 trillion figure come from?
Earth.com’s April 21, 2026 article reports that the figure comes from multiplying a reported 20–40 million metric ton estimate by an approximate U.S. average contract price of about $37,000 per ton for lithium carbonate. That is a secondary-media gross-value calculation, not a published USGS or DOE valuation. The official sources cited here do not state that the deposit is worth $1.5 trillion.
Multiplying an estimated quantity by a product price leaves out the steps and costs between mineral in the ground and a sale. It does not account for how much lithium could actually be recovered, how much could be converted into saleable lithium carbonate, processing capacity, mining and processing costs, the price over the project’s life, or the time value of money. The price reference is also time-sensitive. The resulting headline number is therefore not a mine’s expected revenue, company valuation, or profit.
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What is Thacker Pass, and what stage is it at?
Thacker Pass is a mine and processing project at the southern end of the McDermitt Caldera, about 60 miles (100 km) northwest of Winnemucca, Nevada. It is a development within the larger geological region, not another name for the entire caldera. Lithium Americas’ project overview says the project received a Bureau of Land Management Record of Decision in January 2021 and that initial construction began in early 2023.
Planned capacity is not production
The company says Phase 1 is designed to produce 40,000 tonnes per year of battery-quality lithium carbonate, with mechanical completion targeted for late 2027. These are a design capacity and a company target—not evidence that the facility is already producing that amount or that the target cannot change.
What the federal loan covers
DOE reports that in October 2024 it issued a $2.26 billion direct loan to Lithium Nevada Corp., a Lithium Americas subsidiary. The amount includes $1.97 billion in principal and $289.7 million in capitalized interest. DOE’s environmental-impact-statement project page says the loan concerns lithium-carbonate processing facilities and associated infrastructure, not development and operation of the open-pit mine. The loan is financing information; it is not proof of an economically recoverable reserve or completed production.
Does a large clay deposit mean lithium can be mined profitably?
No. A large geological resource can be important without proving that a particular extraction project will be profitable. USGS notes that lithium is mined from pegmatites, brines, and clays, while international production is dominated by brines. Clay-hosted lithium is a significant geological type, but the presence of lithium in clay does not by itself establish commercially proven extraction at Thacker Pass.
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For a personal-finance reader, the key distinction is between a resource’s estimated contents and the cash flows a project might generate. The headline calculation does not show what can be recovered, at what cost, on what schedule, or at what future lithium price. Those unknowns prevent the $1.5 trillion figure from serving as a reliable measure of the project’s economic value.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What the headline gets right—and wrong
- Right: McDermitt is a major lithium-bearing geological region associated with the ancient Yellowstone hotspot, and USGS describes it as one of the world’s largest deposits.
- Needs qualification: USGS’s approximately 2 million-tonne figure is its estimate for the largest single U.S. lithium resource; DOE’s North American superlative refers specifically to the Thacker Pass site. Neither establishes a worldwide “largest ever” record on directly comparable terms.
- Wrong if read literally: There is no official confirmation here of a mineable reserve worth $1.5 trillion. That figure is an approximate gross-value calculation reported by secondary media, not a proven asset value.
USGS and the Nevada Bureau of Mines and Geology reported a $300,000 mapping effort in the Thacker Pass area in 2023 to improve geological constraints on the distribution and origin of lithium deposits. That work is part of ongoing scientific characterization; it does not turn a resource estimate into a reserve valuation.
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