Lithium is the third-heaviest element on the periodic table, and, as a result, it occurs throughout the universe in varying states. Lithium is highly reactive and highly flammable, in its pure form, so it generally occurs compounded with other minerals such as lepidolite, petalite and amblygonite. Lithium is found in trace amounts in nearly all igneous rocks.
While the element is abundant in stars and throughout the cosmos generally, economically viable concentrations of lithium tend to concentrate in specific locations around the world. According to Western Lithium, 59 percent of commercial lithium is extracted from continental brines that are volcanic in origin. Another 25 percent of the world's lithium is found in hard rocks such as pegmatite and spodumene. Other sources include oil-field brines, geothermal brines and within certain minerals such as hectorite.
These deposits do not occur randomly around the world. Economically viable concentrations of lithium tend to be found in regions with a particular geologic history, such as active volcanism and a history of geothermally active brine upwellings. According to Western Lithium, the largest concentrations of lithium in the world are concentrated in South America, specifically the mountainous nations of Chile and Bolivia. There are also mines in Nevada.