Amethyst
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Mineral NameAmethyst
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorspurple, violet
Transparencytransparent
Type LocalityBrazil
Mineral GroupSilicates
Usesjewelry, collector, spiritual
Associated Mineralscalcite, goethite, hematite
Raritycommon
Description
A large, deep purple amethyst geode, displaying numerous well-formed, terminated crystals growing inwards from a rock matrix.
Geological Context
Amethyst forms in hydrothermal veins and cavities (geodes) within volcanic rocks, where silica-rich fluids containing trace amounts of iron are subjected to natural irradiation.
