mineral
Amethyst
Silicon Dioxide (SiO2) with iron impurities
Hardness: 7 on Mohs scale; Color: Purple, violet; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Purple, violet
- Luster
- Vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Purple, violet; Luster: Vitreous; Crystal Structure: Hexagonal (trigonal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in hydrothermal veins or geodes where silica-rich fluids cool and crystallize in volcanic cavities. Commonly found in basalt or other igneous rocks, dating primarily from the Mesozoic era to present.
Uses & applications
Extensively used in jewelry (faceting, cabochons, beads), decorative objects, and as a popular collector specimen. Historically believed to prevent intoxication.
Geological facts
The purple color comes from irradiation and iron impurities within the quartz lattice. When heated, natural amethyst can turn yellow-orange, often sold as 'burnt' citrine.
Field identification & locations
Identify by its hexagonal crystal habit and distinctive purple hue that is often zoned. Found worldwide with major deposits in Brazil and Uruguay. Collectors look for deep saturation and clarity.
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sedimentary
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Metamorphic
Epidote
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Granite
Granite (Phaneritic intrusive igneous rock)
igneous