Kyanite definitions

A bluish-green to colorless mineral, Al₂ SiO₅ , used as a refractory.

A bluish silicate of aluminum, Al₂SiO₅, that forms in long, thin, bladed crystals that are found in metamorphic rocks.

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.