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Name Origin | Kornerupine stone is named after the Danish geologist Kornerup (1857–1883) |
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Chemical Formula | Mg3Al6(Si,Al,B)5O21(OH) |
Color | Colorless, white, pink, greenish yellow, blue green, sea green, dark green, brown, black. |
Hardness | 6 - 7 on Mohs Scale |
Crystal System | Orthorhombic; crystals prismatic; also fibrous, columnar. |
Cleavage | perfect 2 directions; fracture conchoidal; brittle. |
Specific Gravity (SG) | 3.27 - 3.45; gems are 3.28 - 3.35 |
Pleochroism | pronounced and visible to the naked eye: Sri Lanka; Madagascar: yellowish brown/brown/greenish. Kwale District, Kenya: intense green/light green/ greenish yellow. Greenland: dark green/reddish blue/light blue |
Luster | Vitreous |
Stone sizes |
Most gems are under 5 carats, but occasional large material from Sri Lanka, Burma, or East Africa yields a gem in the 25-39 carats range. Canadian crystals are large (up to 2 inches across) but are not generally cuttable. |
Note: Star kornerupine (first discovered in 1884) also has been found (Mogok, Burma) but is very rare. Kornerupine is generally dark brown or green and not very attractive due to the somber colors. The light green material from Kenya is much more appealing, but the sizes are always small. The color is caused by traces of Fe, Cr, and V. Despite the fact that many stones are in museums and private collections, kornerupine is a rather rare gemstone and, for the collector, worth acquiring when available.
References:
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo Credit:
www.shutterstone.com
1- Color Encyclopedia of Gemstones, Joel E. Arem, VNR publications, New York.
Photo Credit:
www.shutterstone.com
"Kornerupine-162065" by John Sobolewski (JSS) - http://www.mindat.org/photo-162065.html. Licensed under CC BY 3.0 via Commons.