Amethyst
Quartz var. Amethyst · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal; typically prismatic with six-sided terminations or druzy clusters in geodes
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2 with trace elements of Iron (Fe3+)
Formation Process
Hydrothermal; forms in silica-rich solutions at low to moderate temperatures, often filling cavities (vugs) in igneous or metamorphic rocks.
About This Crystal
A translucent to transparent violet variety of quartz. This specimen displays a pale lavender (Rose de France) color with a vitreous luster. It shows internal fracturing and visible iridiscence from internal cleavage planes.
Physical Characteristics
Color: Pale violet; Streak: White; Cleavage: None (has poor indistinct cleavage); Fracture: Conchoidal; 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 (Uniaxial +); Pleochroism: Weak to moderate in shades of purple; Visible iris effect (rainbow) due to internal thin-film interference.
Hardness & Durability
Origin Region
Notable sources include Brazil (Rio Grande do Sul), Uruguay (Artigas), Zambia, and Madagascar. Often found in volcanic basalt geodes.
Hardness & Durability
Mohs Hardness: 7; Toughness: Good; Stability: High, though color can fade with prolonged exposure to high heat or intense sunlight.
Care & Maintenance
Safe to clean with warm soapy water and soft brush. Avoid ultrasonic and steam cleaners if the stone has significant internal fractures. Keep away from prolonged direct sunlight to prevent color fading.
Rarity & Value
Common; Value is determined by color saturation (deep purple is highest), clarity, and cut. This pale specimen is affordable, typically priced between $1-5 per carat for polished stones.
Special Characteristics
Internal 'rainbow' iridescence caused by light interference on internal fracture planes; potential for color zoning (tiger stripes) under magnification.
Lore & History
Historically used by the Ancient Greeks to prevent intoxication (name comes from 'amethystos', meaning 'not drunken'). Associated with the Crown Chakra and believed to promote calm, clarity, and intuition.