Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms with pyramidal terminations; this specimen is tumble-polished (massive habit)
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (modified by trace amounts of Iron and irradiation)
Formation Process
Hydrothermal formation in volcanic geodes or cavities via silicon-rich fluids at low to moderate temperatures
About This Crystal
Violet to purple translucent stone with a vitreous luster. This specimen is a small tumbled pebble approximately 12mm in width, showing slight white internal veil-like inclusions and a smooth polished surface.
Physical Characteristics
Color: Lavender/Purple; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert/none; Tenacity: Brittle
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009; Pleochroism: Weak to moderate purple/reddish-purple; Doubly refractive (uniaxial positive)
Hardness & Durability
Origin Region
Brazil, Uruguay, Zambia, Madagascar (Common in volcanic cavities/geodes)
Hardness & Durability
Mohs Hardness: 7; Good toughness for jewelry; stable for most daily wear but can fade with extreme heat or prolonged direct UV exposure
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners if there are many inclusions. Store away from direct sunlight to prevent color fading.
Rarity & Value
Common; Value depends on color saturation (deeper purple is higher value). Polished tumbles of this size are inexpensive ($1-$5 range). Some may be heat treated to produce Citrine.
Special Characteristics
Color zoning (distinct lighter and darker purple bands) and white 'chevron' or 'feather' inclusions often found in tumbled specimens.
Lore & History
Historically used in Ancient Greece as a charm against intoxication (Greek 'amethystos'). Traditionally associated with the Crown Chakra and believed to promote calm, sobriety, and clarity.