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.