Kyanite occurs in pale to deep blue, or white, grey, or green. Color distribution in crystals may be uneven, with darker blue patches towards the interior. A kyanite crystal has two hardness values on the Mohs scale. It is softer parallel to the direction of the cleavage and harder perpendicular to it.
It is common to find staurolite crystals with kyanite in the host matrix. The cracks in some stones are due to formation at high pressure.
Occurrence
Kyanite is found in metamorphic gneiss and schist, and in pegmatite veins through metamorphic rocks. It may be weathered out into alluvial deposits. Gem-quality crystals are found in Myanmar (Burma), Kenya, Brazil, and the European Alps. Alluvial deposits are found in Kenya, Australia, India, and several places in the USA.
Kyanite Properties
- Specific Gravity: 3.68
- Refractive Index: 1.71-1.73
- Birefringence (DR): 0.017
- Luster: Vitreous to pearly
- Crystal Structure: Triclinic
- Composition: Aluminum silicate
- Hardness: 5 or 7
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