Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as six-sided prisms ending in pyramids, though this specimen is tumbled (rounded/ellipsoidal habit).
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron (Fe3+) and irradiation centers
Formation Process
Hydrothermal; formed in volcanic cavities (geodes) or hydrothermal veins from silica-rich solutions at relatively low temperatures.
About This Crystal
Deep purple to violet color with internal color zoning. This specimen is a polished tumble stone, displaying a vitreous luster and translucent to transparent clarity with visible internal fractures and wispy inclusions.
Physical Characteristics
Color: Violet/Purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but can show weak green or bluish under UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009; Optical Character: Uniaxial (+); Pleochroism: Weak to moderate in shades of purple and reddish-purple.
Hardness & Durability
Origin Region
Prominent sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, Zambia, and Russia.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good (lack of cleavage makes it durable); Stability: Generally stable but prone to fading with prolonged high heat or UV exposure.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if there are many inclusions. Keep away from prolonged direct sunlight to prevent color fading.
Rarity & Value
Common; value is determined by color saturation (deep 'Siberian' purple being most valuable), clarity, and carat weight. Heat treatment to create Citrine is common.
Special Characteristics
Color zoning (tiger stripes), fluid inclusions, and internal feathers. The purple color is caused by natural irradiation of trace iron impurities.
Lore & History
Historically used by ancient Greeks to prevent intoxication (word 'amethystos' means 'not drunken'). Associated with the Crown Chakra and believed to promote calm, clarity, and protection in traditional lore.