Amethyst
Quartz var. Amethyst (IMA-approved mineral species: Quartz) · Semi-Precious Gemstone; Mineral Specimen; Decorative Stone
Crystal System
Trigonal; typically occurs in hexagonal-shaped prismatic crystals often forming geodes or clusters; also found in massive or tumbled form.
Mineral Group
Silicate class; Tectosilicate (framework silicate) subgroup of the Quartz group.
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron (Fe3+) and irradiation-induced color centers
Formation Process
Hydrothermal formation within volcanic geodes or cavities; forms at relatively low temperatures (50-250°C) from silica-rich fluids over geological time.
About This Crystal
Transparent to translucent violet to deep purple variety of quartz. This tumbled specimen displays a vitreous luster, noticeable color zoning (uneven distribution of purple), and internal fractures or veil-like inclusions typical of natural quartz.
Physical Characteristics
Color: Pale lavender to deep royal purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but may show weak blue/green under longwave UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009 (Uniaxial positive); Pleochroism: Weak to moderate in shades of purple and reddish-purple; No dispersion phenomena.
Hardness & Durability
Origin Region
Major sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Zambia, Madagascar, and Russia. Often found in volcanic cavities and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7.0; Toughness: Good (due to lack of cleavage); Stability: Generally stable but can fade with prolonged exposure to high heat or UV/sunlight.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic or steam cleaners if there are many internal reaching fractures; store away from direct sunlight to prevent color fading.
Rarity & Value
Common; Value determined by color depth (deep purple with red/blue flashes is most valuable), clarity, and size; Treatments include heat treatment to turn amethyst into citrine or green prasiolite.
Special Characteristics
Displays color zoning; may contain various inclusions such as 'tiger stripe' patterns, goethite needles, or negative crystals; piezo-electric properties inherent to quartz.
Lore & History
Historically worn by Ancient Greeks to prevent intoxication (from 'amethystos' meaning 'not drunk'); used in royal jewelry for centuries. Traditionally associated with the Crown Chakra, peace, and spiritual protection.
Notes
amethyst