Lepidolite can only form in geochemical environments where high concentrations of lithium are available for mineral formation. Lepidolite is a rare mineral because these geochemical situations rarely occur.

The lithium ion is very small, and it does not readily substitute in other minerals. As a result, it is usually one of the last ions to form minerals during the crystallization of a subsurface magma. As other ions are depleted, the residual fluids of magma crystallization become progressively enriched with lithium.

During the final stages of crystallization, there might finally be a high enough concentration of lithium present to form discrete lithium minerals such as spodumene, lepidolite, and petalite. Elbaite tourmaline is another lithium-bearing mineral that forms in association with lepidolite and other lithium minerals. Other associated minerals include: beryl, cassiterite, cleavelandite, muscovite, quartz, topaz, and a variety of feldspar minerals.

Pegmatites, greisens, and hydrothermal quartz veins are rocks of late-stage magmatic crystallization. They are the rocks where much of the world’s lithium minerals are found. In these rocks, lepidolite occurs as disseminated particles, aggregates of fine grains, “books” of flat sheets, and aggregates of curved sheets. Most deposits of lithium-bearing minerals formed by igneous processes are small pod-shaped deposits of a few hundred to a few thousand tons where hand mining and hand separation are required.

Notable occurrences of lepidolite have been found in Minas Gerais, Brazil; Manitoba, Canada; Honshu, Japan; Madagascar; Ural Mountains, Russia; Skuleboda, Sweden; California, Maine, and New Mexico, United States; and Coolgardie, Western Australia.