Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by rhombohedra
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide with traces of Iron Fe3+)
Formation Process
Hydrothermal; forms in cavities (geodes) of volcanic rock from silica-rich groundwater
About This Crystal
Transparent to translucent purple crystal cluster with vitreous luster and conchoidal fracture
Physical Characteristics
Color: Pale lavender to deep violet; Streak: White; SG: 2.65; Fluorescence: Usually inert
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009; Weak to moderate pleochroism
Hardness & Durability
Origin Region
Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, and Zambia
Hardness & Durability
Mohs hardness: 7.0; Toughness: Good; Highly durable for all jewelry types
Care & Maintenance
Avoid prolonged direct sunlight (fading) and hydrofluoric acid; clean with warm soapy water
Rarity & Value
Common; value depends on color saturation (Deep Siberian) and lack of visible inclusions
Special Characteristics
Color zoning, internal 'tiger stripe' inclusions, and occasionally phantom growths
Lore & History
Ancient Greeks believed it prevented intoxication; traditionally associated with the Crown Chakra