Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal; typically occurs as hexagonal prisms terminated by rhombohedra. In this specimen, it is tumbled and polished, obscuring natural habit.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of iron (Fe3+) and natural irradiation
Formation Process
Hydrothermal; forms from silica-rich solutions in cavities (geodes) of volcanic rocks or within metamorphic veins under low to medium temperatures.
About This Crystal
A polished, tumbled stone exhibiting a deep purple body color with translucent to nearly opaque areas. It shows characteristic color zoning (irregular distribution of color) and a vitreous luster when light reflects off the smooth surface.
Physical Characteristics
Color: Purple to violet; Streak: White; Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.65; Fluorescence: Usually inert but can show weak greenish-blue under longwave UV.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: 0.009; Double Refraction (Uniaxial positive); Weak pleochroism from purple to reddish-purple.
Hardness & Durability
Origin Region
Major sources include Brazil (Rio Grande do Sul), Uruguay, Zambia, and Madagascar. Typically formed in volcanic geodes or hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Good toughness with no cleavage, making it highly durable and suitable for all types of jewelry.
Care & Maintenance
Safe to clean with warm soapy water and soft brushes. Avoid prolonged exposure to direct sunlight as UV radiation can cause the purple color to fade over time. Avoid sudden temperature changes.
Rarity & Value
Common; value depends on color saturation (deeper purple is more valuable) and clarity. Tumbled stones like this are very affordable, while 'Siberian' quality deep purple gems command higher prices.
Special Characteristics
Color zoning is a hallmark of natural amethyst. It may contain multi-phase inclusions or tiger-stripe inclusions (negative crystals).
Lore & History
Historically used in Ancient Greece to prevent intoxication (from 'amethystos', meaning 'not drunken'). It is traditionally associated with the Crown Chakra and believed to promote calm, clarity, and protection.