mineral
Amethyst
Silicon dioxide (SiO2) with iron impurities
Hardness: 7 (Mohs scale); Color: Pale lilac to deep purple; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Pale lilac to deep purple
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 (Mohs scale); Color: Pale lilac to deep purple; Luster: Vitreous (glassy); Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed in hydrothermal veins and cavities (geodes) of igneous rocks (basalt). The purple color is caused by natural irradiation of trace trivalent iron (Fe3+) within the crystal lattice.
Uses & applications
Predominantly used as a gemstone in jewelry, decorative carvings, and as a popular specimen for mineral collectors.
Geological facts
Until the 18th century, amethyst was included in the cardinal gemstones alongside diamond, ruby, emerald, and sapphire. Its name comes from the Greek word 'amethystos', meaning 'not intoxicated'.
Field identification & locations
Identify in the field by its distinct purple hue and hexagonal crystal prisms often terminating in points. Commonly found in Brazil, Uruguay, and Thunder Bay (Canada). Many specimens found in retail shops are slices of massive geodes.
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Mineral
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