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Kunzite

Spodumene
Spodumene-usa59abg.jpg
Walnut Hill Pegmatite Prospect, Huntington, Hampshire County, Massachusetts, US (Size: 14.2 x 9.2 x 3.0 cm)
General
Category Silicate mineral, pyroxene
Formula
(repeating unit)
lithium aluminium silicate, LiAl(SiO3)2
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, kunzite often fluorescent under UV
References

Spodumene is a pyroxene mineral consisting of lithium aluminium inosilicate, LiAl(SiO3)2, and is a 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.

The normal low-temperature form α-spodumene is in the monoclinic system whereas the high-temperature β-spodumene crystallizes in the tetragonal system. The normal α-spodumene converts to β-spodumene at temperatures above 900 °C. Crystals are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.

Spodumene was first described in 1800 for an occurrence in the type locality in Utö, Södermanland, Sweden. It was discovered by Brazilian naturalist Jose Bonifacio de Andrada e Silva. The name is derived from the Greek spodumenos (σποδυμενος), meaning "burnt to ashes," owing to the opaque, ash-grey appearance of material refined for use in industry.

Spodumene occurs in lithium-rich granite pegmatites and aplites. Associated minerals include: quartz, albite, petalite, eucryptite, lepidolite and beryl.


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Wikipedia

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