Amethyst Cluster

Birthstone: February
Chakra: Crown, Third Eye, Etheric
Element: Wind
Known As: Stone of Sobriety
Planet: Jupiter, Saturn, Neptune
Rarity: Common
Resonant Number: 3
Zodiac: Virgo, Sagittarius, Capricorn, Aquarius, Pisces

Category: Silicate Mineral
Crystal Class: Trapezohedral
Crystal System: Trigonal
Dana Classification: 75.01.03.01
Empirical Formula: SiO₂
Name: Amethyst
Space Group: P3221 (no. 154)
Strunz Classification: 04.DA.05
Synonym: Stone of Sobriety

Birefringence: +0.009 (B-G interval)
Cleavage: None
Common Colors: Purple, Violet, Dark Purple
Crystal Habit: Crystalline, Druse, 6-Sided Prism, 6-Sided Pyramidal Termination
Diaphaneity: Transparent, Translucent
Formula Mass: 60.08 gm
Fracture: Conchoidal
Luster: Vitreous, Glassy
Mohs Hardness: 7
Optical Properties: Uniaxial (+), w=1.543-1.545, e=1.552-1.554, bire=0.0090.
Pleochroism: Weak to moderate Purple or Violet
Refractive Index: nω = 1.543–1.553, nε = 1.552–1.554
Streak: White