mineral

Blue Kyanite

Kyanite (Al2SiO5)

Hardness: 4.5 to 5.0 parallel to the long axis and 6.5 to 7.0 perpendicular to it (anisotropic). Color: Blue, often with streaks of white or gray. Luster: Vitreous to pearly. Crystal Structure: Triclinic. Cleavage: Perfect [100], imperfect [010]. Specific Gravity: 3.53 to 3.67.

Hardness: 4
Color: Blue, often with streaks of white or gray
Luster: Vitreous to pearly

Identified March 23, 2026More mineral →

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Physical properties

Formation & geological history

Formed through high-pressure regional metamorphism of clay-rich sedimentary rocks (pelites). It is an indicator mineral of the amphibolite or eclogite metamorphic facies. Found in mica schists, gneisses, and associated pegmatites.

Uses & applications

Used industrially in the manufacture of refractory materials like spark plugs, kiln linings, and high-heat ceramics due to its expansion when heated. It is also used as a semi-precious gemstone in jewelry and is highly sought after by mineral collectors.

Geological facts

Kyanite is a polymorph along with andalusite and sillimanite; all three share the same chemical formula but have different crystal structures. It is one of the few minerals that exhibit two significantly different hardnesses based on the direction of the scratch.

Field identification & locations

Identify in the field by its distinct bladed crystal habit, blue color, and dual hardness test. Commonly found in metamorphic belts in locations such as Brazil, Russia, Switzerland, and the Appalachian Mountains in the USA.