Spodumene

Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate, LiAl(SiO3)2, and is a commercially important source of lithium. It occurs as colorless to yellowish, purplish, or lilac kunzite (see below), or alternatively yellowish-green or emerald-green hiddenite; it takes the form of prismatic crystals, often of great size. Single crystals of 14.3 m (47 ft) in size are reported from the Black Hills of South Dakota, United States. The naturally occurring low-temperature form α-spodumene is in the monoclinic system, and the high-temperature β-spodumene crystallizes in the tetragonal system. α-Spodumene converts to β-spodumene at temperatures above 900 °C. Typically crystals are heavily striated along the principal axis. Crystal faces are often etched and pitted with triangular markings.