Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone and Mineral Specimen
Crystal System
Trigonal, with prismatic crystal habit terminated by rhombohedra
Mineral Group
Silicate, specifically Tectosilicate
Chemical Formula
SiO2
Formation Process
Hydrothermal and low-temperature magmatic processes, precipitating from silica-rich aqueous solutions within cavities of volcanic rocks
About This Crystal
The specimen features a polished, cut-base amethyst geode cluster displaying translucent to transparent purple quartz crystals with characteristic hexagonal terminations and rich color zoning
Physical Characteristics
Purple body color ranging from pale lilac to deep violet, white streak, conchoidal fracture, lack of true cleavage, specific gravity of approximately 2.65, brittle tenacity, and piezoelectric properties
Optical Properties
Uniaxial positive optical character, doubly refractive with a birefringence of 0.009, weak pleochroism showing reddish-purple and bluish-purple shades, and vitreous luster
Hardness & Durability
Origin Region
Brazil, Uruguay, Madagascar, Zambia, and the United States; typically found in volcanic gas cavities and hydrothermal veins
Hardness & Durability
Mohs hardness of 7, good durability for everyday jewelry use though susceptible to thermal shock and scratching by harder minerals like topaz or corundum
Care & Maintenance
Clean with warm soapy water using a soft brush, avoid ultrasonic cleaners and harsh chemicals, and store away from prolonged direct sunlight to prevent color fading
Rarity & Value
Common to moderately rare depending on color saturation and clarity; valued based on deep purple color saturation, transparency, and size, with treatments such as heat treatment into citrine being common
Special Characteristics
Displays natural color zoning, phantom growth lines, and strong piezoelectric properties when subjected to mechanical stress
Lore & History
Historically used by ancient Greeks and Romans to prevent intoxication, associated with royalty, peace, and spiritual growth, and linked traditionally to the third eye and crown chakras