Spodumene | |
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![]() Walnut Hill Pegmatite Prospect, Huntington, Hampshire County, Massachusetts, U.S. (size: 14.2 × 9.2 × 3.0 cm) | |
General | |
Category | Inosilicate |
Formula (repeating unit) | lithium aluminium silicate, LiAl(SiO3)2 |
IMA symbol | Spd[1] |
Strunz classification | 9.DA.30 |
Dana classification | 65.1.4.1 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | C2/c |
Unit cell | a = 9.46 Å, b = 8.39 Å c = 5.22 Å β = 110.17°; Z = 4 |
Identification | |
Color | Highly variable: white, colorless, gray, pink, lilac, violet, yellow and green, may be bicolored; emerald green – hiddenite; lilac – kunzite; yellow – triphane |
Crystal habit | prismatic, generally flattened and elongated, striated parallel to {100}, commonly massive |
Twinning | Common on {100} |
Cleavage | Perfect prismatic, two directions {110} ∧ {110} at 87° |
Fracture | Uneven to subconchoidal |
Tenacity | Brittle |
Mohs scale hardness | 6.5–7 |
Luster | Vitreous, pearly on cleavage |
Streak | white |
Specific gravity | 3.03–3.23 |
Optical properties | Biaxial (+) |
Refractive index | nα = 1.648–1.661 nβ = 1.655–1.670 nγ = 1.662–1.679 |
Birefringence | δ = 0.014–0.018 |
Pleochroism | Strong in kunzite: α-purple, γ-colorless; hiddenite: α-green, γ-colorless |
2V angle | 54° to 69° |
Fusibility | 3.5 |
Solubility | insoluble |
Other characteristics | Tenebrescence, chatoyancy |
References | [2][3][4][5] |
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), yellowish-green or emerald-green hiddenite, 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.[6][7]
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.[5] Crystals are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.[not verified in body]
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