Spodumene
| Spodumene | |
|---|---|
 An almost colorless kunzite crystal (upper left), a cut pale pink kunzite (upper right) and a greenish hiddenite crystal (below) |
|
| General | |
| Category | Mineral |
| Chemical formula | lithium aluminum silicate, LiAl(SiO3)2 |
| Identification | |
| {{{molweight}}} | |
| 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 |
| Refractive index | 1.66-1.68 |
| Pleochroism | Strong in kunzite: pink, colourless; hiddenite: yellow-green, blue-green |
| Streak | white |
| Specific gravity | 3.17-3.19 |
| {{{density}}} | |
| Fusibility | 3.5 |
| Solubility | insoluble |
| Other Characteristics | Tenebrescence, chatoyancy, kunzite often fluorescent under UV |
Spodumene is a pyroxene mineral consisting of lithium aluminum inosilicate and is a source of lithium. It occurs as colorless to yellowish, purplish or lilac kunzite, yellowish-green or emerald-green hiddenite, prismatic crystals, often of great size. Single crystals over 10 m in size are reported from the Black Hills of South Dakota.
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, meaning "burnt to ashes," owing to the opaque, ash-gray appearance of material refined for use in industry.
Occurrence
Spodumene occurs in lithium rich granites and pegmatites. Source localities include Brazil, Madagascar, USA (North Carolina, California), Afghanistan, and Pakistan.
Characteristics
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The chemical formula can be written as LiAl(SiO3)2.
Economic Importance
- Transparent spodumene has long been used as a gemstone with varieties kunzite and hiddenite noted for their strong pleochroism.
Spodumene is an important source of lithium for use in industrial 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. Spodumene is becoming less important a source of lithium due to the emergence of alkaline brine lake sources in China and Argentina, which produce lithium carbonate and lithium hydroxide directly.
Kunzite
Kunzite is a pink to lilac colored gemstone, a variety of spodumene with the colour coming from minor to trace amounts of manganese. Some (but not all) kunzite used for gemstones has been heated to enhance its colour. It was named in honor of New York mineralogist and gemologist George Frederick Kunz. It has been found in Brazil, USA, Canada, CIS, Mexico, Sweden, Western Australia, Afghanistan and Pakistan. <br=clear all>
Hiddenite
Hiddenite is a pale to emerald green variety of spodumene that is sometimes used as a gemstone.
The first specimens of the hiddenite variety of spodumene were recovered about 1879 near the tiny settlement of White Plains, west of Stony Point, Alexander County, North Carolina. According to contemporary accounts, a young man named Lackey brought them to the attention of J.A.D. Stephenson, a local merchant who was also an ardent collector of minerals. Initially, the yellowish to greenish-yellow hiddenites were thought to be gemmy diopside. Stephenson brought the discovery to the attention of exploration geologist William Earl Hidden, who had been commissioned by Thomas Edison to search for any sources of platinum in North Carolina (an effort that was, in and of itself, stunningly unsuccessful). Hidden sent samples of the odd green material to John Lawrence Smith, a prominent chemist and mineralogist of Louisville, Kentucky. Smith correctly identified the specimens as being a variety of spodumene, and named them “hiddenite” in honor of Hidden. The community in which the gemstones were first found would later be renamed "Hiddenite." During the hey-day of hiddenite mining in the 1880s and 1890s it was also known as “lithia emerald.” Hidden recognized the value of the emeralds and the potential of the new gemmy green spodumene. He acquired a tract of poor quality land, which was either the site of the initial discovery or near to it, for $1500. The Emerald and Hiddenite Mining Company was organized and excavations on the site quickly recovered loose hiddenites and emeralds in the red, gravelly clay. At a depth of about 26 feet they struck bedrock and soon were recovering hiddenites from solid rock. Oddly, period newspaper accounts and statements by Kunz (1892) indicate that mining on the site was never undertaken as a full time operation, but was only prosecuted a few weeks or months during the summer. Writing in 1892, Kunz described the hiddenite being recovered as “always transparent, ranges from colorless (rare) to a light yellow, into a yellowish green, then into a deep yellow emerald green. Sometimes an entire crystal has a uniform green color, but generally one end is yellow and the other green.” Kunz noted that the finest crystal recovered prior to 1892 measured 68 mm tall, and could have cut a gem of 5.5ct estimated weight. The size of most cut gems were small, with a 2ct hiddenite in the Augustus C. Hamlin collection being considered amoung the finest of the large stones.
In addition to the North Carolina locality, Hiddenite has also been found in Brazil, China, and Madagascar. Green spodumene found in Afghanistan and Pakistan has excited modest amounts of controversy in the mineral and gemological communities with debate over whether or not it should be truly considered "hiddenite" as well as claims that the green coloration is induced by irradiation and is fugitive.
See also
ReferencesISBN links support NWE through referral fees
- Farndon, John. 2006. The Practical Encyclopedia of Rocks & Minerals: How to Find, Identify, Collect and Maintain the World's best Specimens, with over 1000 Photographs and Artworks. London: Lorenz Books. ISBN 0754815412.
- Klein, Cornelis, and Barbara Dutrow. 2007. Manual of Mineral Science. 23rd ed. New York: John Wiley. ISBN 978-0471721574.
- Palache, C., S.C. Davidson, and E.A. Goranson. 1930. The Hiddenite deposit in Alexander County, North Carolina. American Mineralogist 15:280.
- Pellant, Chris. 2002. Rocks and Minerals. Smithsonian Handbooks. New York: Dorling Kindersley. ISBN 0789491060.
- Schumann, Walter. 2006. Gemstones of the World 3rd ed. New York: Sterling. ISBN 1402740166.
- Shaffer, Paul R., Herbert S. Zim, and Raymond Perlman. 2001. Rocks, Gems and Minerals. Rev. ed. New York: St. Martin's Press. ISBN 1582381321.
- Genth, F. A. 1883. Hiddenite. American Journal of Science 23:68.
External links
- Spodumene Mineral Data. Webmineral.com. Retrieved May 24, 2007.
- Spodumene. Mindat.org. Retrieved May 24, 2007.
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