Actual and potential sources of lithium are from pegmatites, continental brines, geothermal brines, oilfield brines and the clay mineral hectorite.
PEGMATITES - are course grained igneous rocks formed by the crystallization of post magmatic fluids. They occur in close proximity to large magmatic intrusions. Lithium containing pegmatites are relatively rare and are most frequently associated with tin and tantalite. Many of the lithium ‘discoveries’ resulted from the exploration for these associated minerals.
The principal lithium pegmatite minerals are spodumene, petalite (both lithium-aluminium silicates) and lepidolite (a lithium mica) which normally contains minor quantities of cesium, rubidium and fluorine. All have been used directly in the glass and ceramic industries provided the iron content is low and all have been used as the feedstock for the production of lithium chemicals. Spodumene, as a concentrate, is still used in China for lithium chemical production and new production is planned in Europe and Australia.
CONTINENTAL BRINES - these brines with the lithium derived mainly from the leaching of volcanic rocks vary greatly in lithium content largely as a result of the extent to which they have been subject to solar evaporation. They range from between 30 to 60 ppm in the Great Salt Lake, Utah, where the evaporation rates are modest and dilution is constant due to the high volume of fresh water inflow, through the subsurface brines in Searles Lake California (a former location of lithium production) and Silver Peak, Nevada (a current source) to the high altitude salars in Bolivia, Argentina, Chile, Tibet and China where lithium concentrations can be very high.
GEOTHERMAL BRINES - the author is not aware of any publications that provide a listing of the lithium content of all known geothermal brines. Small quantities are contained in brines at Wairakei, New Zealand (13ppm Li) at the Reykanes Field (8ppm) and other areas in Iceland and at El Tatio in Chile (47ppm). The most attractive known occurrences are in the the Brawley area south of the Salton Sea in Southern California.
OILFIELD BRINES - large tonnages of lithium are contained in oil field brines in North Dakota, Wyoming, Oklahoma, east Texas and Arkansas where brines grading up to 700mg/lt are known to exist. Other lithium brines exist in the Paradox Basin, Utah and but the author is unaware of any global review of the potential.
HECTORITE CLAYS - hectorite is a magnesium lithium smectite and the clay is found in a number of areas in the western United States. The largest known deposit is associated with the volcanic rocks of the McDermitt caldera that straddles the Nevada/Oregon border where it occurs in a series of elongate lenses. Current drilling is confirming earlier work that indicated very large tonnages of contained lithium.