The mineral kyanite
is an aluminium silicate
of the sillimanite
group (along with andalusite
), also called alumino-silicate. It has the formula Al2
). Its hardness
varies widely depending on its crystallographic direction, from 5 to 7.5, and it has a specific gravity
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