gemstone
Amethyst
Quartz (SiO2)
Hardness: 7 on the Mohs scale, Color: Purple to violet, Luster: Vitreous, Crystal structure: Trigonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
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Physical properties
Hardness: 7 on the Mohs scale, Color: Purple to violet, Luster: Vitreous, Crystal structure: Trigonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed in gas cavities (vesicles) in volcanic rocks, or as linings in hydrothermal veins, through the precipitation of silica-rich solutions with trace amounts of iron.
Uses & applications
Used primarily in jewelry, ornamental carvings, and as a popular mineral specimen for collectors.
Geological facts
The purple color of amethyst is caused by irradiation and trace amounts of iron impurities substituting for silicon in the crystal lattice. Ancient Greeks believed amethyst could prevent intoxication.
Field identification & locations
Identified by its distinctive purple coloration and high hardness (scratches glass). Commonly found in Brazil, Uruguay, Zambia, and the USA.
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