lepidolite

Lepidolite is a lithium-rich member of the mica group, a layered phyllosilicate mineral. It is typically lilac, pink, or purple and occurs in tabular, plate-like crystals or granular aggregates. The mineral is widely known for its pearly luster and perfect basal cleavage, and it is relatively soft, with a Mohs hardness of about 2.5 to 3.

Chemically, lepidolite is a potassium-rich, lithium-bearing mica. Its structure consists of silicate tetrahedral sheets linked in pairs to form layers that accommodate a octahedral sheet containing aluminum and lithium. The idealized formula is often given as KLi2Al(Si4O10)(OH)2, with fluorine or hydroxyl groups occupying terminal positions. Trace elements such as rubidium, cesium, and manganese can influence color, contributing to its characteristic violet to lavender hues.

Occurrence and formation: Lepidolite forms in granitic pegmatites and certain felsic igneous rocks, frequently in late-stage crystallization with minerals like quartz, feldspar, spodumene, tourmaline, and beryl. It can form large, well-formed crystals and may occur with other lithium-bearing minerals in economically significant deposits.

Uses and significance: Lepidolite is an important lithium-bearing mineral and serves as a minor ore source for lithium, which is used in batteries, ceramics, glass, and lubricants. In jewelry and ornamental use, it is valued for its color and sheen but requires care due to its softness and perfect cleavage.

Etymology: The name derives from Greek lepis, meaning “scale,” in reference to its scaly, plate-like crystal habit.