sedimentary
Geode or Concretion
Silica-filled nodule (likely SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (if quartz/agate center); Color: Dull brownish-gray exterior, potential crystalline interior; Luster: Earthy exterior; Crystal system: Trigonal (if quartz); Cleavage: None.
- Hardness
- 6
- Color
- Dull brownish-gray exterior, potential crystalline interior
- Luster
- Earthy exterior
Identified More sedimentary →
Explore Geode or Concretion in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (if quartz/agate center); Color: Dull brownish-gray exterior, potential crystalline interior; Luster: Earthy exterior; Crystal system: Trigonal (if quartz); Cleavage: None.
Formation & geological history
Formed in sedimentary rock cavities (such as limestone) or volcanic ash beds through groundwater mineral precipitation over millions of years.
Uses & applications
Primarily used as lapidary material, decorative display pieces, or for education/collecting once sliced or cracked open.
Geological facts
Until opened, it is often impossible to know if a geode contains beautiful crystals or is solid (a nodule/thunder egg).
Field identification & locations
Identify by a rounded, bumpy, 'cauliflower' exterior texture that feels lighter than a normal rock of its size. Common in the American Midwest and desert regions.
More like this
Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary