Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal, with a prismatic or massive habit terminated by rhombohedrons
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2
Formation Process
Hydrothermal and magmatic processes, precipitating from silica-rich solutions at low to moderate temperatures within volcanic cavities
About This Crystal
A small, translucent to transparent purple crystal specimen displaying vitreous luster and characteristic violet color zoning with lighter and deeper purple patches
Physical Characteristics
Color ranges from pale lilac to deep purple; white streak; no true cleavage; conchoidal fracture; specific gravity of approximately 2.65; brittle tenacity; exhibits piezoelectricity
Optical Properties
Uniaxial positive optic sign with a refractive index of 1.544 to 1.553 and a birefringence of 0.009; doubly refractive with weak dichroism in reddish-violet and bluish-violet
Hardness & Durability
Origin Region
Brazil, Uruguay, Madagascar, Zambia, and parts of the United States; typically forms in volcanic cavities or hydrothermal veins
Hardness & Durability
Mohs hardness of 7; good durability for jewelry wear though vulnerable to high heat and prolonged direct sunlight
Care & Maintenance
Clean with warm soapy water using a soft brush; avoid harsh chemicals, ultrasonic cleaners, and extended exposure to direct sunlight to prevent color fading
Rarity & Value
Common; value depends primarily on color saturation, transparency, and size, ranging from inexpensive raw specimens to higher-priced gem-grade cuts; heat treatment to yellow citrine is sometimes applied
Special Characteristics
Exhibits piezoelectric and pyroelectric properties; often shows color zoning or phantom growth lines
Lore & History
Historically used by ancient Greeks and Romans as an amulet to prevent intoxication and promote clear-headedness; associated with the third eye and crown chakras in modern crystal healing traditions