Geode
Image: <a href="//commons.wikimedia.org/wiki/User:Cccefalon" title="User:Cccefalon">CEphoto, Uwe Aranas</a> (CC BY-SA 4.0)
Mineral NameGeode
Chemical FormulaSiO2
Mohs Hardness7
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.65
Colorsgreyish-blue, light blue, turquoise, reddish-brown
Transparencytranslucent
Type LocalityUnknown
Mineral GroupSilicates
Usescollector's item, decorative
Associated Mineralsquartz, limonite
Raritycommon
Description
This geode features a cavity lined with numerous botryoidal, greyish-blue to light blue quartz crystals, with small patches of brighter turquoise crystals, all enclosed within a reddish-brown limonite rind.
Geological Context
Geodes typically form in volcanic or sedimentary rocks when mineral-rich water seeps into a pre-existing cavity, depositing layers of minerals, most commonly chalcedony and quartz, over time. The outer shell often consists of iron-rich minerals like limonite.
