sedimentary
Geode
Quartz nodule / Chalcedony-lined cavity
Hardness of 7 on the Mohs scale (for the quartz interior), varies in color from white, grey, brown to translucent, dull outer crust with vitreous or sparkly interior crystals, cryptocrystalline to microcrystalline structure, no distinct cleavage.
Identified More sedimentary →
Explore Geode in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 7 on the Mohs scale (for the quartz interior), varies in color from white, grey, brown to translucent, dull outer crust with vitreous or sparkly interior crystals, cryptocrystalline to microcrystalline structure, no distinct cleavage.
Formation & geological history
Formed in sedimentary or volcanic rocks where groundwater dissolves cavity minerals and deposits silica over millions of years.
Uses & applications
Commonly collected as lapidary specimens, used in decorative items and jewelry making.
Geological facts
Geodes often start as hollow bubbles in volcanic rock or animal burrows in sedimentary rock, gradually filling with mineral-rich water.
Field identification & locations
Found worldwide in limestone formations, volcanic ash beds, and deserts; often identified by their rounded, knobby exterior and hollow, crystal-lined interior when cracked open.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary