mineral
Amethyst
Silicon Dioxide (SiO2) with iron impurities
Hardness: 7 on Mohs scale; Color: Purple/Violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Purple/Violet
- Luster
- Vitreous (glassy)
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Physical properties
Hardness: 7 on Mohs scale; Color: Purple/Violet; Luster: Vitreous (glassy); Crystal Structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Forms in hydrothermal veins and volcanic geodes when silica-rich water cools. The purple color comes from irradiation of iron impurities within the quartz crystal structure.
Uses & applications
Primarily used as a gemstone in jewelry, for decorative carvings, and as a popular specimen for mineral collectors.
Geological facts
Until the 18th century, amethyst was considered one of the five cardinal gemstones alongside diamond, ruby, sapphire, and emerald. Ancient Greeks believed it could prevent intoxication.
Field identification & locations
Identify by its characteristic purple color and hexagonal prism shapes. Commonly found in Brazil, Uruguay, and Zambia. In the field, look for volcanic rock with hollow centers (geodes).
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Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
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Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic