Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal. Typical habit is six-sided prisms ending in pyramids, but this specimen is a tumbled/massive habit.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 with trace amounts of Fe3+ (Iron) and irradiation-induced color centers
Formation Process
Hydrothermal formation within igneous volcanic rocks. Forms as silica-rich fluids deposit crystals in host rock cavities or geodes at relatively low temperatures.
About This Crystal
Deep purple to near-black tumbled stone. Opaque in this thickness but likely translucent at edges. Exhibits a vitreous (glassy) luster with visible lighter-colored internal fractures and inclusions.
Physical Characteristics
Color is dark violet/purple; streak is white; no cleavage; conchoidal fracture; specific gravity 2.65; usually inert under UV but some varieties show weak greenish fluorescence.
Optical Properties
Uniaxial positive; Refractive Index: 1.544–1.553; Birefringence: 0.009; Weak to moderate pleochroism (purple/reddish-purple).
Hardness & Durability
Origin Region
Brazil, Uruguay, Madagascar, and Zambia. Commonly found in volcanic cavities (geodes).
Hardness & Durability
Mohs hardness of 7. Good toughness with no cleavage, making it highly durable for all jewelry types.
Care & Maintenance
Safe with warm soapy water. 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 depth (deep purple is best) and clarity. Tumbled specimens are generally inexpensive.
Special Characteristics
Displays color zoning; may contain primary fluid inclusions or 'tiger stripe' inclusions characteristic of amethyst.
Lore & History
Historically used in Ancient Greece to prevent intoxication (Greek 'amethystos' means 'not drunken'). Associated with royalty and the Third Eye/Crown chakras in traditional healing lore.