Spodumene

Spodumene
An almost colorless kunzite crystal (upper left), a cut pale pink kunzite (upper right) and a greenish hiddenite crystal (below) (unknown scale)
General
Category	Mineral
Chemical formula	lithium aluminium silicate, LiAl(SiO3)2
Identification
Color	Highly variable: white, colorless, gray, pink, lilac, violet, yellow and green
Crystal habit	prismatic, generally flattened and elongated
Crystal system	monoclinic; 2/m
Cleavage	Perfect prismatic, two directions at nearly 90°
Fracture	Sub-conchoidal
Mohs scale hardness	6.5 - 7
Luster	Vitreous
Streak	white
Specific gravity	3.17-3.19
Refractive index	1.66-1.68
Pleochroism	Strong in kunzite: pink, colorless; hiddenite: yellow-green, blue-green
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 metres in size are reported from the Black Hills of South Dakota, United States.

Crystals form in the monoclinic system and are typically heavily striated parallel to the principal axis. Crystal faces are often etched and pitted with triangular markings.

Spodumene 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 granites and pegmatites. Transparent material has long been used as a gemstone with varieties kunzite and hiddenite noted for their strong pleochroism. Source localities include Afghanistan, Australia, Brazil, Madagascar, Pakistan and USA (North Carolina, California).

Economic importance

Spodumene is an important source of lithium for use in ceramics, mobile phone and automotive batteries, medicine and as a fluxing agent. Lithium is extracted from spodumene by fusing in acid.

World production of lithium via spodumene is around 80,000 metric tonnes per annum, primarily from the Greenbushes pegmatite of Western Australia, and some Chinese and Chilean sources. The Talison mine in Greenbushes, Western Australia has an estimated reserve of 13 million tonnes.

Spodumene is becoming a less important a source of lithium due to the emergence of alkaline brine lake sources in Chile, China and Argentina, which produce lithium chloride directly. Lithium chloride is converted to lithium carbonate and lithium hydroxide by reaction with sodium carbonate and calcium hydroxide respectively.

Kunzite

Kunzite
See the pleochroism and the typical etched marks (unknown scale)

Kunzite is a pink to lilac colored gemstone, a variety of spodumene with the color coming from minor to trace amounts of manganese. Some (but not all) kunzite used for gemstones has been heated to enhance its color. It is also frequently irradiated to enhance the color. Many kunzites fade when exposed to sunlight. It was discovered in 1902, and was named after George Frederick Kunz, Tiffany & Co's chief jeweler at the time, and a noted mineralogist. It has been found in Brazil, USA, Canada, CIS, Mexico, Sweden, Western Australia, Afghanistan and Pakistan.

References

Further reading

• Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. Handbook of Mineralogy; Mineral Data Publishing: Tucson, AZ, 1990.
• Hurlbut, Cornelius S.; Klein, Cornelis Manual of Mineralogy, 20th ed., 1985. ISBN 0-471-80580-7.
• Kunz, George Frederick Gems and Precious Stones of North America; Scientific Publishing Company: New York, 1892.
• Palache, C.; Davidson, S. C.; Goranson, E. A. The Hiddenite deposit in Alexander County, N. Carolina. American Mineralogist 1930, 15 (8), 280.
• Template:Last = Webster.