Lepidolite, a silicate of potassium, aluminum and lithium, is a member of a large family of minerals known as micas. Mica is distinctive because of its perfect cleavage, allowing crystals to be split into microscopically thin sheets. Micas are generally green, brown or black; lepidolite is sometimes yellow but most often is pink, a result of its lithium content. It typically occurs in very coarse grained rocks known as granite pegmatites, along with a variety of gem materials such as elbaite (tourmaline) and aquamarine (beryl). Crystals are found in Brazil and California; compact masses of tiny crystals also may occur.