The U.S. Geological Survey estimates that the Appalachian region in the eastern United States contains about 2.3 million metric tons of undiscovered, economically recoverable lithium oxide (Li₂O) in pegmatite deposits. This breaks down to roughly 1.43 million metric tons in the southern Appalachians (concentrated in the Carolinas) and 900,000 metric tons in the northern Appalachians (mainly Maine and New Hampshire).

This figure is a median (50% confidence) probabilistic estimate based on geologic maps, geochemical sampling, geophysical data, tectonic history, and grade-and-tonnage models from known pegmatite deposits. There’s a wide range: for the northern region alone, there’s 90% confidence of at least 90,000 metric tons and a 10% chance of up to 7.4 million metric tons. The estimates were then filtered for economic recoverability using current global mining experience and lithium prices.

At 2025 (or last year’s) U.S. import levels, this resource could theoretically replace 328 years of net lithium imports.

The USGS also frames it in practical terms:

• Enough lithium for batteries in ~130 million electric vehicles.
• Or 1.6 million grid-scale energy storage batteries.
• (Other reports mention potential for hundreds of billions of cellphones or laptops.)

The U.S. was once the world’s dominant lithium producer (e.g., historical pegmatite mining at Kings Mountain, North Carolina), but it now imports a large share of its needs—primarily from Australia (mined) with much processing tied to China. This Appalachian potential, alongside other domestic resources like brines in Arkansas, highlights opportunities for greater mineral security amid rising demand for EVs, grid storage, and electronics. USGS Director Ned Mamula emphasized it as a step toward reclaiming U.S. mineral independence through better mapping, permitting reform, responsible mining standards, and workforce development.

The lithium occurs in pegmatites—coarse-grained igneous rocks similar to granite, formed during ancient mountain-building events. These are “hard-rock” deposits, unlike the brine evaporation methods dominant in South America or some U.S. oilfield brines. Hard-rock mining (crushing, processing spodumene, etc.) is more energy- and capital-intensive but can be viable at scale, as seen in Australia and historical U.S. operations. The region has known lithium-rich districts (18 identified), with some overlap to past mining areas.

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Quantitative Mineral Resource Assessment of Lithium Pegmatite Deposits in the Northern Appalachian Orogen, USA

Published: Natural Resources Research (2026)

Authors: Niki E. Wintzer 
Christopher S. Holm-Denoma, 
Jacob E. Poletti, 
Dalton M. McCaffrey, 
Stanley P. Mordensky, 
Erik R. Tharalson & 
Collin Cronkite-Ratcliff 

DOI: 10.1007/s11053-026-10652-9

Provided: United States Geological Survey

Abstract

Lithium demand is projected to increase more than 48 times by 2040 due to electric vehicle production and other energy storage needs. Most lithium production is outside of the USA, thereby increasing supply chain vulnerability. The combined end use importance and heightened supply risk of lithium make this lightest metallic element a critical commodity to the USA. To mitigate this supply risk, the US Geological Survey is actively assessing lithium deposits in the USA. Herein, we detail an assessment for lithium-mineralized pegmatites in the US northern Appalachian Mountains. Permissive tracts were generated by cross-referencing tectonic and geologic maps and mineral occurrence data with mappable criteria derived from generalized and region-specific lithium pegmatite ore deposit models; tracts were then ranked as having high, medium, or low permissibility. Available geophysical and geochemical data were found to be of minimal utility for this deposit type at the scale of the assessment. The number of undiscovered deposits were estimated and integrated into probabilistic simulations, which included an expanded and updated global grade and tonnage model of pegmatite-hosted lithium ore. The estimated total amount of undiscovered resources for the northern Appalachian Orogen has a median value of 1,410,000 metric tons of Li₂O when considering moderate correlation across sub-regions. At a confidence level of 90%, a resource of at least 90,000 metric tons of Li₂O remains undiscovered, and at a 10% confidence level, a resource of as much as 7,380,000 metric tons Li₂O remains undiscovered. After applying an up-to-date economic filter to convert median contained lithium to recoverable material, a correlated total of 900,000 metric tons of Li₂O may be economically extractable, equating to enough Li₂O to provide the current annual US lithium supply deficit (presently obtained through net imports) for 127 years at 2025 rates of apparent consumption. This period of provision will inevitably shorten with projected increasing consumption rates, emphasizing that further research could be completed to better delineate regions of high lithium resource potential and

Here is a detailed summary of the USGS paper titled “Quantitative Mineral Resource Assessment of Lithium Pegmatite Deposits in the Northern Appalachian Orogen, USA” by N.E. Wintzer and others, published in Natural Resources Research (2026).

The assessment provides probabilistic estimates of undiscovered lithium resources in pegmatite deposits across the northern Appalachian region (roughly latitudes 38°N to 48°N, covering parts of Maine, New Hampshire, Vermont, and other northeastern states).

• Median (50% probability) contained Li₂O: 1,410,000 metric tons (considering moderate correlation across sub-regions).
• 90% confidence (at least): 90,000 metric tons of Li₂O.
• 10% confidence (as much as): 7,380,000 metric tons of Li₂O.

After applying an economic filter (based on current global mining experience, costs, and lithium prices), the median economically recoverable amount is approximately 900,000 metric tons of Li₂O.

This recoverable figure for the North alone equates to roughly 127 years of current U.S. net lithium imports (based on ~7,100 t Li₂O/yr apparent consumption/import reliance in 2025 data).

Most prospective area: Domain 1 (Maine, New Hampshire, and part of Vermont) stands out, with a median contained resource of ~837,000 metric tons Li₂O and recoverable ~530,000 metric tons Li₂O, potentially from just two undiscovered deposits.

USGS scientists used a standard three-part quantitative mineral resource assessment approach:

1. Delineation of permissive tracts — Areas geologically favorable for lithium-bearing (LCT-type) pegmatites, based on:
   • Geologic maps and tectonic history.
   • Geochemical sampling (lithium indicators in stream sediments, soils, etc.).
   • Geophysical data.
   • Known mineral occurrences (thousands of pegmatites exist in the region, though most are simple and not lithium-rich).
2. Estimation of the number of undiscovered deposits — Expert judgment informed by the density and characteristics of known deposits.
3. Grade-and-tonnage modeling — Combined with a newly developed global dataset for lithium pegmatite deposits to simulate resource amounts via Monte Carlo probabilistic methods.

An economic screening step converted “contained” resources into potentially recoverable ones.

The northern assessment complements a separate (or forthcoming) study on the southern Appalachians (focused on the Carolinas region), which estimated ~1.43 million metric tons of economically recoverable Li₂O. Together, they support the widely cited regional total of ~2.3 million metric tons.

Context and Implications

Lithium occurs primarily in spodumene-bearing pegmatites (coarse-grained igneous rocks). These are “hard-rock” deposits requiring mining, crushing, and chemical processing, unlike South American brine operations.

The U.S. has a long history of pegmatite mining in this region (e.g., historical operations in North Carolina and New England), but current domestic production is minimal, with heavy reliance on imports (much of the supply chain influenced by Australia mining and Chinese processing).

This assessment addresses rising demand for lithium-ion batteries in EVs, grid storage, and electronics. Global demand is projected to grow dramatically (e.g., >48x by 2040 in some scenarios).

Important Caveats

These are undiscovered resource estimates, not proven reserves. Realization depends on successful exploration, drilling, metallurgical testing, permitting, infrastructure, and market conditions.

The number of undiscovered deposits is modeled as relatively small (median of ~3 across the entire northern region in some summaries), meaning any large finds would be significant but not guaranteed.

Economic viability can shift with lithium prices, technology improvements, or regulatory changes.

Environmental and community considerations will play a major role in any future development, especially in rural and scenic parts of New England.

The full paper is available via Springer (open access in some cases) or through USGS publications pages. A companion data release includes GIS shapefiles, geochemical data, permissive tract maps, and tabular results.