Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by rhombohedra
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (+ trace amounts of Fe3+ and irradiation)
Formation Process
Hydrothermal; forms in cavities (geodes) of volcanic rocks at low to moderate temperatures
About This Crystal
A violet to deep purple variety of quartz. It appears as a polished translucent sphere with a vitreous luster and possible internal fractures or color zoning.
Physical Characteristics
Color: Purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Generally inert to weak blue
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Very weak (purple/reddish-purple); Doubly refractive
Hardness & Durability
Origin Region
Brazil, Uruguay, Zambia, Madagascar, and Russia
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Highly durable for jewelry but potentially brittle with sharp impact
Care & Maintenance
Safe with warm soapy water; avoid ultrasonic or steam cleaners if there are many inclusions; protect from prolonged direct sunlight to prevent fading
Rarity & Value
Common; Value depends on color saturation (deeper purple is higher value) and clarity; generally affordable
Special Characteristics
Can show color zoning or 'tiger stripe' inclusions; deep purple variants are often heat-treated to produce Citrine
Lore & History
Ancient Greeks believed it prevented intoxication (from 'amethystos', not drunk); historically associated with royalty and the crown chakra
Notes
Purple