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a mineral of the mica group; by structure, classified as a trioctahedral mica. The approximate chemical composition of lepidolite is KLi1,5 Al1,5 [AlSi3O10] (F, OH), with a Li2O content varying between 1.23 and 5.90 percent. Principal admixtures include Fe2+, Mn, Cs, Rb, and Na. Lepidolite crystallizes in the monoclinic system, forming lamellar crystals and fine-grained scaly masses. The color generally varies from pink to pale violet; colorless varieties are rare. Lepidolite has a hardness of 2.5–3.5 on Mohs’ scale and a density of 2,800–2,900 kg/m3. It occurs in granitic pegmatites in association with pink tourmaline, spodumene, albite, cassiterite, and minerals containing Nb and Ta. Lepidolite is rarely found in greisenized granites and hydrothermal formations. Lepidolite ore is a source of Li and its salts; Cs is sometimes also extracted.