sedimentary

Geode

Quartz-lined nodule (SiO2)

Hardness of 7 on the Mohs scale, earthy exterior with a crystalline quartz interior, vitreous luster, amorphous to nodular external form.

Identified November 14, 2026More sedimentary →

Get a report just like this from any photo, free.

Physical properties

Hardness of 7 on the Mohs scale, earthy exterior with a crystalline quartz interior, vitreous luster, amorphous to nodular external form.

Formed in sedimentary or volcanic rock cavities where mineral-rich groundwater precipitated silica over millions of years.

Commonly collected as mineral specimens, cut and polished for decorative bookends, or used in jewelry making.

Geodes start as hollow bubbles in rock formed by animal burrows, tree roots, or gas pockets in lava, slowly growing crystal linings.

Identify in the field by looking for rounded, knobby, or cauliflower-like nodules that sound hollow when gently tapped.

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