Amethyst Geode
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 3.0)
Mineral NameAmethyst Geode
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorspurple, violet
Transparencytransparent
Type LocalityAmetista do Sul, Alto Uruguai region, Rio Grande do Sul, Brazil
Mineral GroupSilicates
Usesjewelry, collector, decorative
Associated Mineralscalcite, goethite, hematite
Raritycommon
Description
A large, dark grey geode with an elongated cavity lined with numerous sparkling, vibrant purple amethyst crystals.
Geological Context
Amethyst forms in volcanic rocks, particularly in basaltic lava flows, where silica-rich fluids deposit quartz crystals within gas cavities (geodes) or veins, with trace iron impurities causing the characteristic purple color.
