Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically hexangular prismatic crystal habit with pyramidal terminations, though this specimen is massive/rough.
Mineral Group
Silicates (Tectosilicates)
Chemical Formula
SiO2 with trace amounts of iron (Fe3+) and natural irradiation
Formation Process
Hydrothermal; forms in silica-rich solutions at low to moderate temperatures, often filling cavities (vugs) in volcanic or metamorphic rocks.
About This Crystal
Deep to light purple translucent specimen with a vitreous to sub-vitreous luster. Features uneven surfaces with some visible color zoning and internal fractures (crazing).
Physical Characteristics
Color: Purple to violet; Streak: White; Cleavage: None; Fracture: Conchoidal to uneven; Specific Gravity: 2.65; Fluorescence: Usually inert but can show weak blue under SW-UV.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Weak pleochroism (purple/reddish-purple); Doubly refractive (uniaxial positive).
Hardness & Durability
Origin Region
Commonly sourced from Brazil, Uruguay, Zambia, and Madagascar. Likely from a hydrothermal vein or volcanic geode environment.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good (no cleavage); Stable for jewelry but sensitive to high heat and prolonged direct sunlight.
Care & Maintenance
Clean with warm soapy water. Avoid ultrasonic cleaners if fractures are present. Store away from sunlight to prevent color fading.
Rarity & Value
Common; value depends on color saturation ('Deep Siberian' is most prized). Rough specimens like this are affordable ($5-$20 depending on weight).
Special Characteristics
Color originates from irradiation of iron impurities. May show color zoning (darker tips, lighter base).
Lore & History
Historically used by Ancient Greeks to prevent intoxication ('amethystos'). Associated with the Crown Chakra and believed to promote calm and clarity.