Lithium Deposits: Pegmatite, Brine and Clay Explained

Lithium deposits are concentrations of lithium rich enough to mine, and almost all of them fall into three families: pegmatites (coarse granitic dykes carrying spodumene, petalite or lepidolite), brines (salty groundwater under dry salt flats, oilfields or geothermal fields), and sedimentary deposits such as lithium clays. The family decides everything else, from how a deposit is found to how the lithium is recovered and what a resource statement should look like.

Try it: Lithium grade converter and contained-lithium estimate →

World demand has grown fast, and battery use now dominates it. The USGS lithium summary for 2026 puts battery use at 88% of global lithium end use, and estimates that world mine output outside the United States rose 31% in 2025 to about 290,000 tonnes of lithium. Reserves stood at about 37 million tonnes and measured and indicated resources at about 150 million tonnes. Those figures are revised every February, so treat them as a dated snapshot and check the latest edition before quoting them.

“Closed-basin brines hold about 58% of the world’s identified lithium resources, according to the USGS.”

The main types of lithium deposits

The USGS critical-minerals chapter on lithium, Professional Paper 1802-K, splits present and potential lithium sources by deposit type. Closed-basin brines account for about 58% of identified resources, pegmatites (including lithium-enriched granites) about 26%, lithium clays (hectorite) about 7%, and oilfield brines, geothermal brines and lithium zeolites (jadarite) about 3% each. Those shares come from a 2012 compilation, so they describe the geology rather than the current market.

Why mineral grade matters

Lithium minerals carry very different amounts of the metal. The USGS table gives spodumene 3.73% lithium by weight, lepidolite 3.58%, petalite 2.09%, jadarite 3.38% and hectorite only 0.54%. That is why a hectorite clay has to be mined and leached in bulk, while a spodumene pegmatite can be concentrated into a saleable product. It also explains why lithium ore deposits are usually reported in % Li₂O for hard rock and in parts per million or milligrams per litre for brines, so comparing two projects starts with getting the units straight.

Pegmatite lithium deposits: hard rock

Hard rock lithium deposits are almost all lithium-cesium-tantalum (LCT) pegmatites. These are very coarse-grained granitic rocks made mostly of quartz, feldspar and muscovite, with spodumene, petalite or lepidolite as the lithium carriers and, in the richer ones, tantalum, tin, cesium and beryllium minerals as well. The USGS notes that the biggest spodumene crystal yet found, from South Dakota, is 14 metres long, and that the Tanco pegmatite in Manitoba contains 105 identified minerals.

The USGS deposit model for LCT pegmatites describes where they form. They sit in the metamorphic hinterlands of old mountain belts, typically in upper greenschist to lower amphibolite facies rocks, and are generally emplaced within 10 km of a fertile, peraluminous granite. The parent granite may not even be exposed. Around it, pegmatites are zoned: common pegmatites sit close to the granite and the most lithium-rich ones sit farthest out. The same model names Tanco in Canada, Greenbushes in Australia and Bikita in Zimbabwe as giant deposits, with Greenbushes holding the largest lithium and tantalum resource of any LCT pegmatite.

They are small targets

Even the biggest pegmatite lithium deposits are small next to the granites that feed them. The USGS describes Greenbushes as about 3 km long and a few hundred metres across, while typical granite plutons cover more than 10 km². Exploring a pegmatite district is therefore a search for narrow dykes and swarms within a halo several kilometres wide, and much of the work is ruling ground out.

Ages point to the best belts

LCT pegmatites formed in pulses that match times when continents were colliding into supercontinents. The USGS lists age peaks at 2,638, 1,809, 962, 485, 309, 274 and 97 million years, and says the potential for giant deposits looks greatest in Archean (older than 2,500 million years) collision zones. That is one reason the Archean cratons of Western Australia, Canada’s Superior Province and Zimbabwe dominate lithium pegmatite exploration.

How lithium pegmatite exploration works

Lithium pegmatite exploration follows a fairly settled sequence. It starts with the belt (age and metamorphic grade), narrows to fertile granites, then to the pegmatite swarm around them, and finally to individual dykes worth drilling. The USGS paper gives a useful example of how far weathering spreads the signal: at Greenbushes, arsenic, beryllium, antimony and tin form a halo about 12 by 20 km in lateritic soils, and niobium, tantalum and boron form a smaller halo about 1 by 5 km. Cassiterite, tantalite, elbaite and spessartine are dense and durable enough to find by panning stream sediments.

1. Desktop: geology maps, age data, magnetics and radiometrics, satellite imagery and elevation data to outline granites, contacts and structures.
2. Reconnaissance: stream-sediment and heavy-mineral sampling, rock chips from every pegmatite outcrop.
3. Soil grids: lithium plus pathfinders (Cs, Rb, Ta, Sn, Be, As) over the most promising sector.
4. Mapping and trenching: dyke orientation, zoning and the lithium mineral present.
5. Drilling: diamond core to confirm thickness, grade and mineralogy, then metallurgical test work.

The chart shows why hard rock matters commercially even though brines hold more of the resource. By the USGS count, seven mineral operations in Australia, five in Zimbabwe, two in Mali (see our guide to Africa’s lithium deposits), two in Canada and one in Brazil were among the main contributors to 2025 output, alongside brine operations in Argentina and Chile and both kinds in China. Australia alone mined about 92,000 tonnes, mostly from the spodumene pegmatites of Western Australia.

Lithium brine deposits: salars, oilfields and geothermal fluids

Lithium brine deposits are bodies of saline groundwater enriched in dissolved lithium. The producing continental deposits have average concentrations of 160 to 1,400 ppm and estimated resources of 0.3 to 6.3 million tonnes of lithium, according to the USGS. They share a checklist: an arid climate, a closed basin with a salt lake or salt flat, subsidence driven by tectonics, igneous or geothermal activity, lithium-bearing source rocks, one or more aquifers to hold the brine, and enough time to concentrate it.

Clayton Valley in Nevada, producing since the 1960s, is the best-studied example, and one of the lithium deposits in the United States we cover separately. It covers only about 100 km² and holds about 0.3 million tonnes of lithium, yet it shows the whole process: brine averaging 160 ppm is pumped through nine evaporation ponds covering 16 km², and it takes nearly two years to reach about 5,000 ppm. The Salar de Atacama in Chile is the giant of the type, covering about 2,100 km² with brine averaging 1,400 ppm.

Where lithium brine deposits form

The most important single test is whether the basin is closed. If rainfall rises enough for the lake to overflow its divide, the lithium drains away with the water. The USGS places favourable zones between about 19° and 37° latitude north or south, and notes that all but one known lithium-brine basin shows signs of high heat flow such as young volcanoes, hot springs or geothermal fields. Borate deposits and glassy volcanic tuffs are favourable indicators, and a hectorite halo can be all that remains of a brine that has leaked away.

Oilfield and geothermal brines

Deep oilfield brines can carry several hundred ppm lithium. The USGS cites Smackover Formation brine in the US Gulf Coast with up to 692 mg/L in a limestone about 200 m thick at 1,800 to 4,800 m depth. The drawbacks are depth, since these brines usually sit more than 1 km down, and climate, since solar evaporation does not work outside arid regions. Geothermal brines add heat to the picture, and the Salton Sea area of California is the example the USGS gives.

Lithium clay deposits and other sedimentary lithium deposits

Lithium clay deposits hold about 7% of identified resources in the USGS breakdown. The clays analysed from the western United States are enriched in magnesium, fluorine and lithium together, which points to hydrothermal alteration. Hectorite, a smectite clay with about half a percent lithium, is the most widespread, but lithium-rich illite and illite-smectite mixtures also occur.

The largest sedimentary lithium deposits found so far sit in old volcanic lake beds. The USGS singles out the Kings Valley hectorite deposit inside the McDermitt caldera complex in northern Nevada, where lithium clays occur in hydrothermally altered lake sediments that once filled the caldera, and where leaching with sulfuric acid has proven feasible. Every lithium clay occurrence in the Basin and Range shares three traits: lake sediments, volcanic ash or other volcanic material, and hydrothermal alteration.

Zeolites, borates and the Turkey connection

The only documented lithium-zeolite deposit is at Jadar in Serbia, where layers of jadarite, a boron-lithium silicate, reportedly several metres thick, grew in Miocene lake beds. On USGS estimates it holds about 3% of world lithium resources on its own. In Turkey, the Bigadiç borate deposit contains associated hectorite, and the USGS lists mineral-based lithium sources in development or exploration in Turkey and Thailand among many other countries. Borates matter for exploration because they share the same hot-spring-and-lake setting as lithium clays.

“Greenbushes, the largest LCT pegmatite lithium resource, is only about 3 km long, the USGS notes.”

Lithium reserves and resources by country

Lithium reserves are the part of the resource that is demonstrated and economic to extract. The USGS 2026 table puts Chile first at 9.2 million tonnes of lithium, then Australia at 8.4 million, China at 4.6 million, and Argentina and the United States at 4.4 million each. For Australia the USGS adds that reserves compliant with the JORC Code or equivalent were 5.1 million tonnes, a reminder that different agencies count on different bases.

Resources are far bigger. Measured and indicated lithium resources total about 150 million tonnes worldwide, with Argentina at 28 million, Bolivia at 23 million, Chile at 13 million and Australia and China at 10 million each. The United States reports 30 million tonnes across continental brines, claystone, geothermal brines, hectorite, oilfield brines and pegmatites. Large lithium deposits are therefore not rare in total; what is scarce is ground that can be permitted, drilled and processed at a cost the market will pay.

Reading a resource statement

• Check the unit. % Li₂O, % Li, ppm Li and tonnes LCE are all in use. The converter above handles the arithmetic.
• Check the category. Inferred resources are not reserves, and an exploration target is neither. Our guide to inferred, indicated and measured resources explains the ladder.
• For brines, look for specific yield measured from drilling, not assumed porosity.
• For clays, look for leach recoveries from test work, because contained lithium means little without them.
• ⚠ Beware of totals that mix types, such as a pegmatite in % Li₂O added to a brine in tonnes LCE.

Lithium exploration: methods by deposit type

The USGS makes a point worth repeating to anyone raising money for lithium exploration: the search for lithium has never been as intense as the search for gold deposits or copper, so it is likely that large, economic deposits remain to be found. The methods differ sharply by deposit type, and so does what a lithium exploration company should be able to show at each stage.

What lithium exploration companies disclose

Lithium exploration companies range from juniors with a few claims over a pegmatite swarm to producers drilling brine fields next to their plants. Whatever the size, investors should expect the deposit type stated plainly, grades in a stated unit, the lithium mineral identified, and for brines the specific yield and pumping data. Our round-up of gold, uranium and lithium exploration companies covers how juniors in these metals differ.

Lithium deposit terms in plain English

Spodumene

A lithium-aluminium silicate with 3.73% lithium, the main ore mineral in hard rock lithium deposits. Sold as concentrate, often quoted at 6% Li₂O.

Petalite and lepidolite

Other pegmatite lithium minerals. Petalite carries about 2.1% lithium and lepidolite, a lithium mica, about 3.6%.

Salar

A salt flat or salt-encrusted depression in a closed basin, the surface expression of many lithium brine deposits.

Specific yield

The share of an aquifer’s volume that will drain as brine under gravity. It, not total porosity, is what CIM guidance uses to estimate a brine resource.

LCE

Lithium carbonate equivalent, the tonnage of lithium carbonate a given amount of lithium would make. One tonne of lithium is about 5.3 t LCE.

Fertile granite

A granite whose chemistry shows it could have fed lithium-rich pegmatites: high in cesium, rubidium, tin and tantalum, low in calcium, iron and magnesium.

Common mistakes with new lithium discoveries

Most early disappointments in lithium follow a handful of patterns, and nearly all of them could have been caught with cheap work before the drill rig arrived.

• Assuming every white pegmatite carries lithium. Most pegmatites near a granite are barren; the lithium-rich ones are usually the distal dykes.
• Assaying for lithium only, and missing tantalum, tin or cesium that can change the economics of hard rock lithium deposits.
• Skipping mineralogy, so lithium held in micas or clays is counted as if it were spodumene.
• Treating a surface brine sample as a grade for a whole basin, when concentration can change sharply with depth and aquifer.
• Ignoring water rights in brine and clay projects until after the resource is drilled.

Lithium deposits by region: guides in this series

Each region has its own mix of deposit types, regulators and data. This hub sits under our mineral exploration guide, and the regional guides below go deeper, one market at a time.

• Lithium in Mali, Zimbabwe and the rest of Africa: the pegmatite belts of Mali, Zimbabwe, Nigeria, Ghana and the Democratic Republic of the Congo, and the export and ownership rules that shape them.
• Lithium in Alberta and across Canada: oilfield brines in Alberta and Saskatchewan, and the pegmatites of Quebec, Ontario and Manitoba, including the Georgia Lake field north-east of Thunder Bay.
• US lithium deposits: Nevada’s brines and clays, the Kings Mountain pegmatite belt, Smackover brines and Salton Sea geothermal fluids.
• Lithium in Argentina and the lithium triangle: the salars of the Puna and their neighbours in Chile, Bolivia and Peru.
• Australian lithium: the spodumene pegmatites of Western Australia’s Pilbara and Yilgarn cratons.

Lithium often travels with other battery metals in the same belts. For graphite, nickel, cobalt and vanadium, see our battery-metals exploration guide.

How satellite screening fits lithium exploration

Satellite data suits the first stage of lithium exploration for every deposit type. For pegmatites it helps map granite phases, contacts, structures and the outcrop pattern of dyke swarms over a whole licence. For brines and clays it helps outline closed basins, salt crusts, old shorelines, alteration and volcanic source rocks. Our satellite-based mineral detection analyses multispectral and hyperspectral data over your area to flag target zones, alteration halos, faults and fractures. Lithium is on our published list of detectable materials, along with the tantalum and niobium that often accompany it in pegmatites.

• Input: coordinates, KML/KMZ or a polygon, plus country and target mineral.
• Output: high-potential zones, prospectivity heatmaps, estimated location and depth ranges, geological interpretation, PDF and GIS files.
• ✔ Time and cost: 5–20 business days; early-exploration timelines cut from months to days and costs lowered by up to 80–85%.
• Premium+: TargetMax™ drilling-angle recommendations and 3D subsurface models.

We have scanned 100,000+ hectares for 20+ mineral types across 25+ countries. Results are exploration targets to be tested by mapping, sampling and drilling, not resources. Draw your licence on mining.farmonaut.com (Map Your Mining Site), ask for a scope through the mining query form, or view a sample of satellite-driven 3D mineral prospectivity mapping.

Frequently asked questions

Reviewed September 2026 against the USGS Mineral Commodity Summaries 2026 lithium chapter, USGS Professional Paper 1802-K on lithium, the USGS deposit model for lithium-cesium-tantalum pegmatites, CIM’s best-practice guidelines for lithium brines and the Ontario Mineral Inventory record for the Georgia Lake pegmatites.

Production, price, reserve and resource figures are USGS estimates revised every February; check the latest edition. Deposit-type shares date from a 2012 compilation. Nothing here is investment advice. Satellite targets are exploration targets, not mineral resources, and need sampling and drilling to confirm.