Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs in hexagonal-appearing prismatic habit with rhombohedral terminations. Often found as druzy or within geodes.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide with trace amounts of Iron Fe3+)
Formation Process
Hydrothermal formation within the cavities of volcanic rocks (geodes) or veins. Color is produced by gamma irradiation of trace iron impurities post-crystallization.
About This Crystal
Transparent to translucent purple crystals with a vitreous (glassy) luster. Shows characteristic color zoning with deeper purple at the tips and lighter or clear quartz at the base. Visible rhombohedral crystal faces.
Physical Characteristics
Color: light lilac to deep royal purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but may show weak greenish-blue under UV light.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Weak to moderate in shades of purple and reddish-purple; Optical character: Uniaxial positive.
Hardness & Durability
Origin Region
Notable sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, Zambia, and Russia. Found in volcanic basalt vugs and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Stability: Stable to most chemicals but sensitive to high heat and prolonged direct sunlight which can cause color fading.
Care & Maintenance
Clean with warm soapy water and a soft brush. Ultrasonic cleaners are generally safe if there are no liquid inclusions. Avoid steam cleaning and prolonged exposure to UV/sunlight to prevent fading.
Rarity & Value
Common to Uncommon for high quality. Value is determined by color intensity (the deeper the purple, the higher the value), clarity, and lack of visible zoning. Deep 'Siberian' purple is most prized.
Special Characteristics
May contain 'tiger stripe' inclusions or liquid-filled cavities. Features distinct color zoning. Some specimens exhibit dichroism under polarized light. Piezoelectric properties characteristic of all quartz.
Lore & History
Ancient Greeks believed it prevented intoxication (the name comes from 'amethystos' meaning 'not drunk'). Historically considered a Cardinal Gem until the 18th century. Associated with the crown chakra and high spiritual consciousness in traditional lore.