Difference between revisions of "Kyanite"
(submission from Joel Andersson and Ylva Larsson)
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Blue to , blue-green and brown.
Kyanite has directional hardness with 5
Kyanite has directional hardness with 55 in the direction of the c-axis and 7 in right angles to the c-axis.
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colourless, blue, darkblue.
Revision as of 05:17, 28 May 2007
|Chemical composition||Aluminum Silicate Al2Si05|
|Habit||Elongated bladed or columnar.|
|Cleavage||Perfect and good/uneven|
|Hardness||4 - 7.5|
|Optic nature||Biaxial -|
|Refractive index||1.710- 1.734|
|Specific gravity||3.65 - 3.68|
|Pleochroism||Moderate to Strong, Trichroic|
Kyanite is an aluminiumsilicate with the chemical formula Al2SiO5. Its name derives from the Greek word "kyanos" wich means blue.
The colour is blue to colourless, blue-green and brown with vitreous lustre.
Kyanite together with andalusite and silimanite, all gemstones, belongs to the same polymorphic family. All are isolated tetrahedral silicates and have the same chemical formula but have distinctly different structures.
Kyanite is a metamorphic mineral that occours in schists, gneisses and granite pegamatites. Associated minerals are quartz, feldspar, mica, garnet, corundum and staurolite.
Kyanite occurs as bladed and tabular triclinic crystals. Lamellar twinning is common. It has two cleavage directions, one perfect and the other one good-uneven. It has directional hardness with 5,5 in the direction of the c-axis and 7 in right angles to the c-axis.
Localities: Brazil, Kenya, Mocambique, Norway, Myanmar, Austria, Switzerland etc.
Blue to colorless, blue-green and brown.
Kyanite has directional hardness with 4 to 5.5 in the direction of the c-axis and 7 in right angles to the c-axis.
Moderate to strong: colourless, blue, darkblue.
LW-UV: Weak red.
Absorptionspectra: (706), (689), (671), (652), 446, 443.
- Gems sixth edition (2006) - Michael O'Donoghue ISBN 0750658568
- Gemstones of the world 13th edition (2006) - Walter Schuman
- Mineralogy second edition (2002) - Dexter Perkins ISBN 0130620998