Flint geode
Image: <bdi><a href="//commons.wikimedia.org/wiki/User:ComputerHotline" title="User:ComputerHotline">Thomas Bresson</a></bdi> (CC BY 3.0)
Mineral NameFlint geode
Chemical FormulaSiO2
Mohs Hardness6.5
Crystal Systemtrigonal
Lustervitreous
Streak Colorwhite
Cleavagenone
Fractureconchoidal
Specific Gravity2.6
Colorswhite, grey, pale yellow, brown
Transparencytranslucent
Mineral GroupSilicates
Usescollector, historical tools
Associated Mineralscalcite, dolomite
Raritycommon
Description
A nodule of light-colored, cryptocrystalline flint with a central cavity lined with small, sparkling, pale yellowish-white quartz crystals.
Geological Context
Flint geodes form in sedimentary rocks, typically limestone or chalk, where silica-rich fluids replace carbonate material and later deposit quartz crystals within internal voids.
