Image of Kyanite
Kyanite

ID: 90

Kyanite

Chemical Formula

Al2SiO5

Hardness (Mohs)

~5 parallel to the length of the blades, ~7 perpendicular to the length

Crystal System

Triclinic

Streak

White

Luster

Vitreous to pearly

Diaphaneity

Transparent to translucent

Color

Typically blue, but can also be white, gray, green, or even black. Often shows color zoning.

Crystal Habit / Mode of Occurrence

Typically long, bladed crystals, often in radiating or parallel aggregates.

Fun Facts

Kyanite is known for its unusual property of having significantly different hardness depending on which direction you scratch it on the crystal face. This makes it a diagnostic property for identification.