Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by two sets of rhombohedra; the specimen shown is a tumbled, water-worn, or polished pebble habit.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron (Fe3+) and irradiation effects
Formation Process
Hydrothermal; forms from silica-rich solutions in cavities of volcanic rocks (geodes) or hydrothermal veins at relatively low temperatures (50-250°C).
About This Crystal
Deep purple to violet body color. The specimen is a polished, tumbled stone with a vitreous (glassy) luster. It exhibits transparent to translucent zones with some internal fractures or white quartz veining (chevron-like patterns).
Physical Characteristics
Color: Violet to dark purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Weak/inert (can be dull green or blue under UV).
Optical Properties
Uniaxial positive; Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Weak to moderate purple/reddish-purple; no chatoyancy or asterism present in this specimen.
Hardness & Durability
Origin Region
Major sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, Zambia, and Russia. Likely from a hydrothermal vein or geode environment.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good (though brittle); Stability: Sensitive to high heat (can turn yellow/orange); very wearable for all types of jewelry.
Care & Maintenance
Clean with warm soapy water. Avoid steam cleaners or ultrasonic cleaners due to potential internal fractures. Store away from direct, prolonged sunlight as the color can fade over time.
Rarity & Value
Common; Value is determined by color saturation ('Deep Siberian' purple is most valuable) and clarity. Tumbled stones like this are very affordable, typically sold by weight or for a few dollars.
Special Characteristics
Color zoning is common. This specimen shows potential white quartz banding or internal veil-like inclusions typical of 'Chevron Amethyst' varieties.
Lore & History
Historically used by Ancient Greeks to prevent intoxication (ame-thystos meaning 'not drunk'). Associated with the Crown Chakra; traditionally believed to promote calm, clarity, and spiritual protection.