Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically occurs in a hexagonal prismatic habit with pyramid-like terminations or as massive, crystalline aggregates within geodes.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2 (Silicon Dioxide) with trace impurities of Iron (Fe4+) and irradiation
Formation Process
Hydrothermal formation within cavities of volcanic rocks (basalt). Silica-rich water precipitates at low to moderate temperatures (50–300°C), while natural gamma radiation from surrounding rocks colors iron impurities purple.
About This Crystal
The specimen is a rough, crystalline fragment showing a characteristic violet to purple color. It exhibits a vitreous (glassy) luster on fresh surfaces and ranges from translucent to transparent. The color appears somewhat uneven, which is typical for natural amethyst, showing patches of darker and lighter violet.
Physical Characteristics
Color: Pale to deep violet; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like) to uneven; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Typically inert, but some may show weak bluish or greenish glow under UV.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Optically Uniaxial (+); Pleochroism: Weak to moderate in shades of purple and reddish-purple.
Hardness & Durability
Origin Region
Notable sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Madagascar, Zambia, and Russia. Found commonly in volcanic amygdules and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 7; Toughness: Fair to good; Stability: Stable to light but may fade with prolonged exposure to high heat or intense direct sunlight (UV).
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic or steam cleaners if the stone has significant fractures. Store away from intense sunlight to prevent color fading and keep separate from harder stones like diamonds or sapphires.
Rarity & Value
Rarity: Common; Value Factors: Deep, uniform violet color (Siberian quality) is most prized. Large, clear specimens are affordable compared to precious stones. Treatments: Heat treatment is common to produce 'citrine' (orange) or green quartz (prasiolite).
Special Characteristics
May show color zoning, liquid or gas-filled inclusions (two-phase inclusions), and occasionally 'tiger striped' internal fractures or goethite/hematite inclusions.
Lore & History
Historically, the name comes from the Greek 'amethystos', meaning 'not drunken', as it was believed to prevent intoxication. In lore and healing, it is associated with the Crown Chakra and is traditionally symbolical of peace, protection, and spiritual clarity.