Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by rhombohedra; frequently found in geode or druzy habits
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of Iron (Fe3+) and natural irradiation
Formation Process
Hydrothermal formation within cavities of volcanic rock (basalts) or metamorphic environments at relatively low temperatures
About This Crystal
A violet to purple variety of quartz. This specific specimen is a tumbled, translucent pebble showing light-to-medium purple color zoning, vitreous luster, and internal veils or fractures
Physical Characteristics
Color: Purple to violet; 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; Pleochroism: Very weak (purple/reddish-purple); Uniaxial positive
Hardness & Durability
Origin Region
Brazil, Uruguay, Zambia, Madagascar, and Russia; typically found in volcanic geodes or hydrothermal veins
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Highly durable for jewelry but can be brittle if heavily included
Care & Maintenance
Clean with warm soapy water; avoid prolonged exposure to direct sunlight as it may fade; sensitive to high heat and hydrofluoric acid
Rarity & Value
Common; Value is driven by color depth (Siberian purple is most valuable) and clarity; heat treatment is common to produce citrine
Special Characteristics
Color zoning is typical; may contain 'tiger stripe' inclusions or needle-like goethite; exhibits piezoelectric properties
Lore & History
Ancient Greeks believed it prevented intoxication (amethystos means 'not drunk'); historically associated with royalty and the Crown Chakra; used as a protective amulet throughout the Middle Ages