Kyanite in Quartz

Physical Properties

Hardness: 4.5 to 7 (anisotropic: 4.5 parallel to length, 7 perpendicular); Color: Blue blades with clear/white matrix; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in one direction.

Formation & Geological History

Formed through the regional metamorphism of clay-rich sedimentary rocks under high pressure and relatively low temperatures. Commonly found in schists and gneisses.

Uses & Applications

Used in the manufacture of refractory products (high-heat porcelain/ceramics), spark plugs, and as a semi-precious gemstone in jewelry or collector clusters.

Geological Facts

Kyanite is unusual because its hardness varies significantly depending on the direction of the scratch test. It is a blue polymorph of aluminosilicate, sharing the same chemistry as sillimanite and andalusite.

Field Identification & Locations

Identify by the elongated, bladed crystal habit and distinct blue color. Found in high-grade metamorphic terrains like the Appalachian Mountains, Brazil, and India.

Identified on: 4/19/2026

Mode: Standard