Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by rhombohedra. This specimen is a tumbled/polished pebble.
Mineral Group
Silicates (Tectosilicate subgroup / Quartz group)
Chemical Formula
SiO2 (Silicon Dioxide) with trace impurities of Fe3+ (Iron)
Formation Process
Hydrothermal; forms in cavities (geodes) of volcanic rocks (basalt) or in hydrothermal veins at low to moderate temperatures.
About This Crystal
A deep violet to purple transparent gemstone with a vitreous (glassy) luster. This specific piece is a small, polished 'tumble stone' exhibiting a smooth, rounded surface.
Physical Characteristics
Color: Deep purple. Streak: White. Cleavage: None. Fracture: Conchoidal. Specific Gravity: 2.65. Diaphaneity: Transparent to translucent. Fluorescence: Typically inert.
Optical Properties
Refractive Index: 1.544–1.553. Birefringence: 0.009. Pleochroism: Weak purple to reddish-purple. It is doubly refractive (uniaxial positive).
Hardness & Durability
Origin Region
Notable sources include Brazil, Uruguay, Zambia, and Madagascar. Most commercial tumbled stones originate from Brazil.
Hardness & Durability
Mohs Hardness: 7. Toughness: Good (suitable for daily wear). Stability: Stable but can fade upon prolonged exposure to intense UV/sunlight.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if there are fractures. Store away from direct sunlight to prevent color fading.
Rarity & Value
Common. Value factors include color saturation (deep purple is most prized) and clarity. Tumbled specimens are inexpensive, often sold by weight.
Special Characteristics
May exhibit color zoning or 'tiger stripe' inclusions under magnification. The purple color is the result of irradiation of trivalent iron (Fe3+) in the quartz lattice.
Lore & History
Ancient Greeks believed it prevented intoxication (amethystos means 'not drunk'). Historically associated with royalty and the Third Eye or Crown chakras in modern spiritual practices.