Blue Kyanite

Physical Properties

Hardness: 4.5-5.0 along crystals, 6.5-7.0 across (Anisotropy); Color: Blue, translucent; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect; Specific gravity: 3.53 - 3.67

Formation & Geological History

Formed during regional metamorphism of clay-rich sedimentary rocks under high pressure. It is a polymorphic mineral that shares a chemistry with Andalusite and Sillimanite but forms at higher pressures.

Uses & Applications

Used industrially in the production of refractory materials (ceramics, bricks, mortar) for high-temperature furnaces. In jewelry, it is used for cabochons and beads, and it is a popular specimen for crystal collectors.

Geological Facts

Kyanite is highly unusual because its hardness varies significantly depending on the direction it is scratched; it is much softer parallel to its long axis than perpendicular to it.

Field Identification & Locations

Identify by its characteristic bladed crystal habit and variable hardness. Found commonly in mica schists and gneisses in Brazil, Nepal, Switzerland, and the USA (North Carolina). Collectors should look for the flat, bladed texture shown here.

Identified on: 4/18/2026

Mode: Standard