Kyanite

Kyanite is a member of the aluminosilicate family - which also includes its polymorphs silimanite and andalusite (polymorphs have the same chemical formula but a different crystalline strucutre). Kyanite has the chemical formula Al2SiO5. [1]

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Kyanite
Kyanite
Photo by Aelwyn - released under Creative Commons 2.5 License

Kyanite derives its name from the Greek kuanos, meaning deep blue - and this is its most common color; although shades of blue-green, grey, brown and white are sometimes seen. Additionally, there is a rare colorless variety, which has been found in Machakos, Kenya. [2] It is occasionally seen in bright orange, green or black forms. The orange variety is a recent discovery, having been found in Tanzania in 2007. [3]

One of kyanite's key identifying characteristics is anisotropism - meaning that its hardness is markedly different on different axes of direction of the crystals. This quality is only found in a very few minerals. Kyanite's hardness is 4.5-5 in the direction of the crystal's long axis, and 6.5-7 on a perpendicular axis (i.e. "across" the crystal). [1] [4] Kyanite is brittle, and this can cause difficulty in cutting the stones, which may be prone to breakage along the length of the crystal.

Kyanite was named in 1789 by noted mineralogist Abraham Gottlieb Werner. It also has several other names, which include cyanite (the French spelling), disthene and rhaeticite. These are however far less commonly used. The name "disthene" means "two strengths" and was the old name for the stone. [5]

Kyanite is somewhat more likely to be seen in a mineral / crystal collection than as a cut gemstone: It is brittle and has perfect cleavage, which means that it breaks too easily in one direction. However, it is nonetheless quite often faceted, or seen cut en cabochon. [6] Looking around online at prices (January 2011), I am seeing kyanite gemstones in the 5-15 carat range, priced at between $15 and $32 per carat.

Kyanite has industrial uses - including being used in the manufacture of high temperature ceramics (such as those used in spark plugs), porcelain, abrasives and electronics. [1] Much of the kyanite used industrially goes towards the manufacture of refractory materials, which are used to make furnace materials by industries such as steel and glass. The refractory material is created by the calcining (a thermal treatment process) of kyanite at temperatures of around 1350-1380o C. [7]

Kyanite is found in a large number of locations around the world - including Australia, Austria, Brazil, Canada, China, France, Germany, Italy, Norway, Russia, Switzerland and the USA. [8] It has been found in association with sorundum, andalusite and staurolite. [2]

Kyanite is polymorphous with the minerals andalusite and sillimanite. This means that these minerals all share the same chemical composition, but have different crystal structure.

In folklore, kyanite is associated with bringing calm and tranquility to the wearer. It is also said that kyanite may assist the wearer in developing a better awareness of their general health. [2]

Kyanite Images

Kyanite - Sources Referenced:

[1] http://en.wikipedia.org/wiki/Kyanite
[2] http://www.jewelsforme.com/Kyanite.asp?amp;gemtype=GS
[3] http://www.associatedcontent.com/article/2730453/orange_kyanite_the_hot_new_gemstone.html
[4] http://www.galleries.com/minerals/silicate/kyanite/kyanite.htm
[5] http://geology.com/minerals/kyanite.shtml
[6] http://www.realgems.org/list_of_gemstones/kyanite.html
[7] http://minerals.usgs.gov/minerals/pubs/commodity/kyanite
[8] http://www.mindat.org/min-2303.html

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