mineral
Amethyst
SiO2 (Silicon Dioxide with iron impurities)
Hardness: 7 (Mohs scale), Color: Purple/Violet, Luster: Vitreous (glassy), Crystal Structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: Purple/Violet, Luster: Vitreous (glassy), Crystal Structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture)
Formation & geological history
Forms in hydrothermal veins or as linings inside volcanic geodes. The purple color is caused by irradiation of iron impurities within the quartz structure.
Uses & applications
Widely used in jewelry (faceting, cabochons), as decorative display pieces, and in crystal collection.
Geological facts
Amethyst was once considered a Cardinal Gem, as valuable as diamonds, until large deposits were found in Brazil. Its name comes from the Greek 'amethystos', meaning 'not intoxicated'.
Field identification & locations
Identified by its distinctive purple hue and hexagonal crystal habits. Common in Brazil, Uruguay, and Madagascar. Look for conchoidal fractures and lack of cleavage.
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Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Sandstone with Mineral Veining or Crust
Sedimentary Sandstone (mostly SiO2 with Fe2O3 tinting)
sedimentary
Schist
Schist
Metamorphic
Potassium Feldspar (Orthoclase)
Orthoclase (KAlSi3O8)
mineral
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic