Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone
Crystal System
Trigonal crystal system; typically forms in hexagonal prismatic habits with pyramidal terminations; often found as geode linings or massive clusters.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace amounts of Iron (Fe3+)
Formation Process
Primarily hydrothermal; forms when silica-rich fluids cool in cavities (vugs) within igneous or sedimentary rocks. The purple color results from natural irradiation of iron inclusions within the quartz lattice.
About This Crystal
A violet to purple variety of quartz. This specific specimen is a tumbled or water-worn translucent fragment showing a vitreous luster, uneven color distribution (color zoning), and a slightly irregular shape approximately 2cm in length.
Physical Characteristics
Color: Pale violet to deep purple; Streak: White; Cleavage: None; Fracture: Conchoidal/Uneven; Specific Gravity: 2.65; Fluorescence: Usually inert but can show weak green or blue under UV.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Pleochroism: Weak to moderate purple and reddish-purple; Uniaxial positive.
Hardness & Durability
Origin Region
Major sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Zambia, and Madagascar. Often found in volcanic basalt cavities or hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Stability: Stable to light but may fade with prolonged exposure to extreme UV; Sensitive to high heat which can turn it yellow/orange (Citrine).
Care & Maintenance
Clean with warm soapy water and a soft brush; ultrasonic cleaning is usually safe for untreated stones. Avoid steam cleaning. Store away from direct sunlight and harder gems like Topaz or Diamonds.
Rarity & Value
Common; Value is determined by color saturation (deep 'Siberian' purple is most valuable), clarity, and size. Generally affordable, ranging from $2-$50 per carat depending on quality.
Special Characteristics
Often exhibits color zoning (alternating light and dark layers) and can contain 'tiger stripe' or 'thumbprint' inclusions known as Brewster's fringes.
Lore & History
Historically worn by Ancient Greeks to prevent intoxication (from 'amethystos', meaning 'not drunken'). Highly valued in royal jewelry and religious regalia. Associated with the Crown Chakra and believed to promote calmness and clarity.