sedimentary

Quartz Geode

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, clear to brownish-yellow color, vitreous luster, and hexagonal crystal structure with no true cleavage.

Identified November 11, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, clear to brownish-yellow color, vitreous luster, and hexagonal crystal structure with no true cleavage.

Formed when mineral-rich groundwater deposits silica inside hollow cavities of sedimentary or volcanic rocks over millions of years.

Used widely in decorative displays, gemstone carving, lapidary arts, and sought after heavily by mineral collectors.

Geodes appear as ordinary, bumpy spheres on the outside, but reveal a sparkling crystalline interior when cracked open.

Easily identified by its hollow, crystal-lined center and spherical, nodular exterior found commonly in limestone formations worldwide.

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

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)