Kyanite in Quartz

Physical Properties

Hardness: 4.5–5 parallel to crystal length and 6.5–7 perpendicular to it; Color: Pale to deep blue crystals in a clear/white matrix; Luster: Vitreous to pearly; Crystal structure: Triclinic (bladed crystals); Cleavage: Perfect in one direction.

Formation & Geological History

Formed through high-pressure regional metamorphism of clay-rich sedimentary rocks, typically found in schists and gneisses. It exists in the aluminosilicate polymorph group alongside andalusite and sillimanite.

Uses & Applications

Used in the manufacture of refractory products like high-temperature ceramics and kilns; occasionally used as a gemstone (cabochons) and highly popular among mineral collectors.

Geological Facts

Kyanite is one of the few minerals that exhibits a significant variation in hardness depending on the direction of the scratch (anisotropy). It is known as the 'index mineral' for determining the depth and pressure of metamorphic activity in Earth's crust.

Field Identification & Locations

Identify in the field by its distinct bladed crystal habit, typical blue color, and dual hardness. It is commonly found in Brazil, Switzerland, Russia, and several states in the US like North Carolina and Connecticut.

Identified on: 4/19/2026

Mode: Standard