kyanite

noun

1. a mineral, aluminum silicate, Al2SiO5, occurring in blue or greenish bladed triclinic crystals, used as a refractory.

noun

1. a grey, green, or blue mineral consisting of aluminium silicate in triclinic crystalline form. It occurs in metamorphic rocks and is used as a refractory. Formula AL 2 SiO 5

1. A bluish-green to colorless triclinic mineral. Kyanite occurs as long, thin, blade-shaped crystals in metamorphic rocks. It is unique among minerals in having two grades of hardness, one along its length, and one along its width. It is a polymorph of andalusite and sillimanite, but can form at lower temperatures than either of these. Chemical formula: Al2SiO5.