Dysten

DYSTEN, (ang. disthene), kyanite. Its name derives from the Greek words: dí(s) 'double' + sthénos 'strenght, power'). It is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. Disthene is a diagnostic mineral of the Blueschist Facies of metamorphic rocks.

Disthene is a member of the aluminosilicate series, which includes the polymorph andalusite and the polymorph sillimanite. Disthene is strongly anisotropic, in that its hardness varies depending on its crystallographic direction. While this is a feature of almost all minerals, in disthene this anisotropism can be considered an identifying characteristic.

Disthene is used primarily in refractory and ceramic products, including porcelain plumbing fixtures and dinnerware. It is also used in electrical insulators and abrasives. An interesting property of disthene is that it undergoes an irreversible expansion when fired at high temperature. Disthene has also been used as a gemstone, though this use is limited by its anisotropism and perfect cleavage. Finally, as with most minerals, disthene is a collector's mineral.