Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal crystal system; typically forms in hexagonal prismatic habits but seen here as a tumbled, massive form.
Mineral Group
Silicates (Subgroup: Tectosilicates)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of Iron (Fe3+)
Formation Process
Primarily hydrothermal; forms when silica-rich fluids fill cavities (vugs/geodes) in igneous rocks, crystallizing at low to moderate temperatures.
About This Crystal
A translucent to transparent violet gemstone. This specimen is tumbled and polished, showing a deep purple hue with visible internal fractures and a vitreous (glassy) luster.
Physical Characteristics
Color: Violet to purple; Streak: White; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Generally inert, occasionally weak bluish under UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009; Pleochroism: Weak to moderate in shades of reddish-purple and bluish-purple.
Hardness & Durability
Origin Region
Prominent sources include Brazil, Uruguay, Zambia, and Madagascar. Often found in volcanic geodes or hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Highly durable for everyday jewelry use and scratch-resistant against most household dust.
Care & Maintenance
Clean with warm soapy water. Avoid prolonged exposure to direct sunlight as colors may fade. Safe from most chemicals but sensitive to hydrofluoric acid.
Rarity & Value
Common; Value is driven by color saturation (deep purple being most valuable) and clarity. Large quantities are produced in South America.
Special Characteristics
May exhibit color zoning or 'tiger stripe' inclusions. When heated, it can transform into Citrine or 'Prasiolite' (green quartz).
Lore & History
Historically used by Ancient Greeks to prevent intoxication ('amethystos' means 'not drunk'). In crystal healing, associated with the Crown Chakra and calming energies.