Mineral description : Sillimanite

Sillimanite from Stakholmen.
Sillimanite from Kölaberget.

Chemical formula Al2SiO5
Hardness 6-7
Density 3.2
Color Grey, brown to light green.
Crystal form Ortorombic. Long and thin crystals.
Luster Glas or silk.
Description .
Habitat Quite common in Sweden, as a ingredience in granites and gneiss. Larger aggregates are not so common. Also at the borderzones of pegmatites.
Associates .
Notes All three disten minerals are used to high temperature cheramics as in sparkplugs.
Polymorphs : Kyanite and Andalusite
Sillimanite is created at temperatures higher than 550 degrees C and in all pressures.
Locations
  • Kolsva feldspar mine, at the borderzone of the pegmatite. In yellow fibric aggregates together with garnet and biotite.
  • Långfallsgruvan Grangärde in Dalarna.
  • Malmberget in Norrbotten.
  • Stakholmen, Hassela.
  • Kölaberget, North of Hälsingland.

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axelsson@acc.umu.se
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Last changed : 1998-03-07