Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by two sets of rhombohedrons; often in druzy crusts or within geodes.
Mineral Group
Silicates (Tectosilicate subgroup / Quartz group)
Chemical Formula
SiO2 (Silicon Dioxide) with traces of Iron (Fe4+) and natural irradiation
Formation Process
Hydrothermal; forms from silica-rich solutions in cavities of volcanic rock. The purple color is caused by trace amounts of iron incorporated into the crystal lattice, which is subsequently irradiated by gamma rays from surrounding rocks.
About This Crystal
Exhibits a range of purple hues from pale lilac to deep violet. Often transparent to translucent with a vitreous (glass-like) luster. Small, interlocking crystals typically form a druzy surface or lined cavity.
Physical Characteristics
Color: Violet to purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but may show weak greenish or bluish tones under UV.
Optical Properties
Uniaxial (+); Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Weak to moderate in purple and reddish-purple tones; Dispersion: 0.013.
Hardness & Durability
Origin Region
Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, Zambia, and Russia (Ural Mountains). Found in volcanic basalt vugs and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good (no cleavage); Stable for daily jewelry wear, though high heat can cause color change.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if the stone has liquid inclusions. Protect from prolonged direct sunlight to prevent color fading.
Rarity & Value
Common; Value is determined by color saturation ('Siberian' deep purple is most prized), clarity, and lack of zoning. Generally affordable, ranging from $2 to $50+ per carat.
Special Characteristics
Color zoning is very common (stripes of darker and lighter purple); can contain liquid inclusions, 'tiger stripe' fracures, or goethite inclusions; turns into Citrine or 'Prasiolite' if heat-treated.
Lore & History
Derives from the Greek 'amethystos' (not drunk), as ancient Greeks believed it prevented intoxication. Historically used in royal jewelry and ecclesiastical rings. Associated with the Crown Chakra and thought to promote sobriety and calm.