sedimentary

Geode

Quartz nodule (SiO2)

Hardness of 7 on the Mohs scale, earthy brown exterior with a dull luster, rounded nodular structure, and no cleavage.

Identified November 13, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, earthy brown exterior with a dull luster, rounded nodular structure, and no cleavage.

Formed through the infiltration of mineral-rich groundwater into cavities within sedimentary or volcanic rocks over millions of years.

Popular in rock collecting, lapidary arts, decorative home displays, and metaphysical crystal healing.

Unbroken geode nodules look like ordinary, unassuming rocks on the outside, hiding hollow crystal-lined interiors.

Found worldwide in limestone formations and volcanic ash beds; identified by a relatively lightweight feel due to internal hollowness when shaken.

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

Sandstone or Siltstone

Arenite (if sandstone)

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Shale

Fissile Sedimentary Rock

Sandstone

Arenite

Shale

Clastic sedimentary rock