Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as six-sided prismatic crystals ending in six-sided pyramids; also found in geodes and massive forms
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron (Fe3+) and natural irradiation
Formation Process
Found in hydrothermal veins and basaltic geodes; forms when silica-rich solutions cool and crystallize in rock cavities over millions of years
About This Crystal
A violet to purple variety of quartz; transparent to translucent with a vitreous (glass-like) luster; color can be zoned and ranges from pale lavender to deep royal purple
Physical Characteristics
Color: Purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but can show weak greenish-blue under UV
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Doubly refractive (uniaxial positive); Pleochroism: Weak to moderate purple/red-purple
Hardness & Durability
Origin Region
Major sources include Brazil (Rio Grande do Sul), Uruguay, Zambia, Madagascar, and Russia; found in volcanic geodes and hydrothermal veins
Hardness & Durability
Mohs Hardness: 7; Good toughness and stability for daily wear; no cleavage makes it resistant to chipping
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic cleaners if there are liquid inclusions; keep away from prolonged direct sunlight to prevent color fading
Rarity & Value
Common; value is determined by color saturation ('Siberian' deep purple is most valuable), clarity, and cut; heat treatment is common to turn it into citrine
Special Characteristics
Color-zoning is frequent; may contain 'tiger stripe' inclusions; can show dichroism and occasionally phantoms or goethite inclusions
Lore & History
Historically used by ancient Greeks to prevent intoxication ('amethystos' means 'not drunk'); traditionally associated with the Crown Chakra, peace, and protection