spodumene

{{Infobox mineral | name = Spodumene | category = Inosilicate minerals (single chain) | group = Pyroxene group, clinopyroxene subgroup | boxwidth = | boxbgcolor = | image = Spodumene-usa59abg.jpg | caption = Walnut Hill Pegmatite Prospect, Huntington, Hampshire County, Massachusetts, U.S. (size: 14.2 × 9.2 × 3.0 cm) | formula = lithium aluminium silicate, LiAl(SiO3)2 | IMAsymbol = Spd | strunz = 9.DA.30 | dana = 65.1.4.1 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c | unit cell = a = 9.46 Å, b = 8.39 Å c = 5.22 Å β = 110.17°; Z = 4 | color = Highly variable: white, colorless, gray, pink, lilac, violet, yellow and green, may be bicolored; emerald green – hiddenite; lilac – kunzite; yellow – triphane | habit = prismatic, generally flattened and elongated, striated parallel to {100}, commonly massive | twinning = Common on {100} | cleavage = Perfect prismatic, two directions {110} ∧ {10} at 87° | fracture = Uneven to subconchoidal | tenacity = Brittle | mohs = 6.5–7 | luster = Vitreous, pearly on cleavage | refractive = nα = 1.648–1.661 nβ = 1.655–1.670 nγ = 1.662–1.679 | opticalprop = Biaxial (+) | birefringence = δ = 0.014–0.018 | pleochroism = Strong in kunzite: α-purple, γ-colorless; hiddenite: α-green, γ-colorless | 2V = 54° to 69° | streak = white | gravity = 3.03–3.23 | melt = | fusibility = 3.5 | diagnostic = | solubility = insoluble | diaphaneity = | other = Tenebrescence, chatoyancy | references = }} 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 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.