Spodumene

Spodumene
Walnut Hill Pegmatite Prospect, Huntington, Hampshire County, Massachusetts, U.S. (size: 14.2 × 9.2 × 3.0 cm)
General
CategoryInosilicate
Formula
(repeating unit)
lithium aluminium silicate, LiAl(SiO3)2
IMA symbolSpd[1]
Strunz classification9.DA.30
Dana classification65.1.4.1
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupC2/c
Unit cella = 9.46 Å, b = 8.39 Å
c = 5.22 Å
β = 110.17°; Z = 4
Identification
ColorHighly variable: white, colorless, gray, pink, lilac, violet, yellow and green, may be bicolored; emerald green – hiddenite; lilac – kunzite; yellow – triphane
Crystal habitprismatic, generally flattened and elongated, striated parallel to {100}, commonly massive
TwinningCommon on {100}
CleavagePerfect prismatic, two directions {110} ∧ {110} at 87°
FractureUneven to subconchoidal
TenacityBrittle
Mohs scale hardness6.5–7
LusterVitreous, pearly on cleavage
Streakwhite
Specific gravity3.03–3.23
Optical propertiesBiaxial (+)
Refractive indexnα = 1.648–1.661 nβ = 1.655–1.670 nγ = 1.662–1.679
Birefringenceδ = 0.014–0.018
PleochroismStrong in kunzite: α-purple, γ-colorless; hiddenite: α-green, γ-colorless
2V angle54° to 69°
Fusibility3.5
Solubilityinsoluble
Other characteristicsTenebrescence, 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]

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Spodumene, Mindat.org
  3. ^ Anthony, John W., Bideaux, Richard A., Bladh, Kenneth W., and Nichols, Monte C. (1990). Handbook of Mineralogy. Mineral Data Publishing, Tucson, Arizona
  4. ^ Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
  5. ^ a b Deer, Howie and Zussman, Rock Forming Minerals, v. 2 Chain Silicates, Wiley, 1963 pp. 92–98
  6. ^ Schwartz, G. (1928). "The Black Hills Mineral Region". American Mineralogist. 13: 56–63.
  7. ^ Robert Louis Bonewitz, 2005, Rock and Gem, London, Dorling Kindersley