mineral
Amethyst
Silicon dioxide with iron impurities (SiO2)
Hardness: 7 (Mohs scale), Color: Purple/Violet, Luster: Vitreous (glassy), Crystal structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Purple/Violet, 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) within igneous rocks. The purple color comes from gamma irradiation of trace iron atoms within the quartz crystal lattice.
Uses & applications
Primarily used in jewelry, as a semi-precious gemstone, for decorative ornaments, and highly valued by mineral collectors.
Geological facts
Amethyst was considered a 'Cardinal Gem' until large deposits were found in Brazil in the 1700s. Its name comes from the Greek 'amethystos', meaning 'not intoxicated', as it was believed to prevent drunkenness.
Field identification & locations
Identify by its distinctive purple color and hexagonal crystal habit if raw. Found commonly in Brazil, Uruguay, and Madagascar. In the field, look for purple crystals inside basaltic geodes.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
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Schist
Metamorphic
Epidote
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metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
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