Kyanite

The mineral kyanite is an aluminium silicate of the sillimanite group (along with andalusite and sillimanite), also called alumino-silicate. It has the formula Al₂O₃·SiO₂ (Al₂SiO₅). Its hardness varies widely depending on its crystallographic direction, from 5 to 7.5, and it has a specific gravity of 3.56-3.67.

It is translucent, usually blue, but possibly white, gray, green, or black. It is usually found in long-bladed crystals or columnar to fibrous structures.

Kyanite is used in refractory and ceramic products. Noted deposits are found in Brazil, USA (North Carolina and Georgia), Switzerland, Russia, India and Kenya. Kyanite is found in such metamorphic rocks as gneiss and schist. The name "kyanite" is derived from the Greek word for "blue."

See also: List of minerals