Blue Kyanite

Physical Properties

Hardness: Anisotropic (4.5 to 5.0 parallel to the long axis and 6.5 to 7.0 across), Color: Blue to white/translucent, Luster: Vitreous to pearly, Crystal Structure: Triclinic with bladed habit, Cleavage: Perfect in one direction.

Formation & Geological History

Formed during the high-pressure regional metamorphism of clay-rich sedimentary rocks. It is a polymorphic mineral that shares the same chemistry as Andalusite and Sillimanite but forms under different pressure-temperature conditions.

Uses & Applications

Used in the manufacturing of refractory materials (heat-resistant ceramics), spark plugs, and cutting wheels. Also popular as a semi-precious gemstone and as a metaphysical/collectible mineral specimen.

Geological Facts

Kyanite is unusual because its hardness varies significantly depending on the direction of the scratch (anisotropy). It is one of the index minerals used by geologists to estimate the depth and pressure at which a rock metamorphosed.

Field Identification & Locations

Identify in the field by its distinct bladed crystal habit, blue color, and directional hardness. Commonly found in metamorphic schist and gneiss in regions like Brazil, Nepal, and the Appalachian Mountains.

Identified on: 4/13/2026

Mode: Standard