Kyanite

Birthstone: April, May
Chakra: Throat, Third Eye
Element: Air, Aether, Water
Known As: Stone of Attunement
Planet: Uranus, Moon
Rarity: Common
Resonant Number: 4
Zodiac: Aries, Taurus, Libra, Pisces

Category: Nesosilicate
Chemical Formula: Al₂SiO₅
Crystal Class: Pinacoidal
Crystal System: Triclinic
Name: Kyanite
Space Group: P1
Strunz Classification: 9.AF.15
Unit Cell: a = 7.1262(12) Åb = 7.852(10) Åc = 5.5724(10) Åα = 89.99(2)°, β = 101.11(2)°γ = 106.03(1)°; Z = 4

Cleavage: [100] perfect [010] imperfect with 79° angle between
Crystal Habit: Columnar, Fibrous, Bladed
Diaphaneity: Transparent to translucent
Fracture: Splintery
Luster: Vitreous
Optical Properties: Biaxial (-)
Pleochroism: Trichroic
Refractive Index: nα = 1.712 - 1.718 nβ = 1.720 - 1.725 nγ = 1.727 - 1.734
Specific Gravity: 3.67
Streak: White
Tenacity: Brittle
Twinning: Lamellar on {100}