Geode
Image: James St. John (CC BY 2.0)
Mineral NameGeode
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorsoff-white, light brown, yellowish-white
Transparencyopaque
Type Localitysouthern Kentucky, USA (possibly)
Mineral GroupSilicates
Usescollector, decorative
Associated Mineralsquartz
Raritycommon
Description
This image shows a subspherical geode with a rough, light brown to off-white exterior. An opening reveals a cavity lined with numerous small, yellowish-white, granular quartz crystals.
Geological Context
Geodes are crystal-lined cavities formed when mineral-rich water enters a void in a host rock, precipitating crystals over time. This specific geode is possibly from the Fort Payne Formation.
