sedimentary
Geode / Fossilized Gastropod or Shell Cast
Silicon dioxide (Quartz) replacement / fossil mold
Hardness of 7 (for the quartz lining), earthy to vitreous luster, amorphous to cryptocrystalline exterior with microcrystalline quartz crystals lining the inner cavity, conchoidal fracture.
Identified More sedimentary →
Explore Geode / Fossilized Gastropod or Shell Cast in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 7 (for the quartz lining), earthy to vitreous luster, amorphous to cryptocrystalline exterior with microcrystalline quartz crystals lining the inner cavity, conchoidal fracture.
Formation & geological history
Formed in sedimentary environments where shells or cavities in rock are slowly dissolved and replaced by mineral-rich groundwater precipitating silica over millions of years.
Uses & applications
Collectible specimen, lapidary arts, metaphysical uses, and educational displays.
Geological facts
Fossilized shells and hollow nodules often act as natural traps for mineral precipitation, resulting in hollow rocks lined with sparkling quartz or chalcedony crystals.
Field identification & locations
Identify by its hollow interior, crystal-lined cavity, and external weathered sedimentary crust. Often found in limestone formations, riverbeds, and desert regions worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary