Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal, typically forming prismatic crystals terminating in rhombohedra, though often found as massive or geode fillings.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2
Formation Process
Hydrothermal and magmatic processes, precipitating from silica-rich solutions at low to moderate temperatures within gas cavities in volcanic rocks.
About This Crystal
A tumbled, smooth pebble showing a pale to medium purple coloration, characteristic of amethyst. It is translucent with a waxy to vitreous luster, lacking distinct crystal faces due to being tumbled into a rounded shape.
Physical Characteristics
Body color is purple (ranging from light lilac to deep violet); streak is white; cleavage is absent; fracture is conchoidal; specific gravity is approximately 2.65; tenacity is brittle; exhibits piezoelectric properties.
Optical Properties
Singly refractive to anomalously doubly refractive, uniaxial positive; refractive index is 1.544-1.553; birefringence is 0.009; typically non-pleochroic or very weakly pleochroic in pale shades.
Hardness & Durability
Origin Region
Brazil, Uruguay, Madagascar, Zambia, and the United States. Forms typically in volcanic rock cavities or hydrothermal veins.
Hardness & Durability
Mohs hardness of 7; good durability for daily wear in jewelry, though prone to scratching softer stones and can fracture under sharp impacts due to lack of cleavage.
Care & Maintenance
Clean with warm soapy water using a soft brush; avoid ultrasonic cleaners and harsh chemicals; store away from direct prolonged sunlight to prevent the purple color from fading.
Rarity & Value
Common; value is determined by color saturation, clarity, and size, with deep purple specimens commanding higher prices. Heat treatment to yellow (citrine) or green (prasiolite) is common.
Special Characteristics
May exhibit color zoning in raw specimens; piezoelectric properties; sometimes displays weak blue or red fluorescence under longwave UV light.
Lore & History
Historically used by ancient Greeks and Romans as an amulet to prevent intoxication. Associated with the third eye and crown chakras in modern crystal healing, symbolizing peace, clarity, and spiritual growth (traditional beliefs, not scientific claims).