Mineral description : Kyanite

Kyanite from Stora Akersvatnet, Norway.

Kyanite are created in the temperature- pressure area at all pressures above 0 at 250 degrees C to pressures above 9 kbar at 750 degrees C.
As a rarity sometime clear crystals of kyanite is used in jewellery, both as cabochones and facetted stones.
Chemical formula Al2SiO5
Hardness 4-5 along the cleavage plane and 6-7 across.
Density 3.67
Color Light blue.
Crystal form Triclinic. Forms long bladed crystals or radially aggregates.
Luster glas.
Description
Optical properties Weak pleocroism.
Habitat Appears only in highly metamorphic rocks, never in eruptive rocks. The crystals grows in quartz jugs that lies in the dark metamorphic schist.
Associates Often with staurolite in the schist. Sometimes with beryl and rutil in the quartz jugs.
Notes Looks like topas, but topas occurs in pegmatites, where kyanite never exists.
Polymorphs : Andalusite and Sillimanite
Locations
  • In quartz jugs at Hegset in the Nea valley, Norway.
  • Kyanite are mined at Horrsjöberg, Värmland (together with lazulite, pyrophyllit, and brown rutil).
  • Västanå, Skåne ( with lazulite ).
  • Dicksberget Värmland.

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axelsson@acc.umu.se
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Last changed : 1998-03-08