sedimentary

Cannonball Concretion

Calcite-cemented sandstone concretion

Hardness 6-7 on the Mohs scale, grey to brown color, dull luster, amorphous or cryptocrystalline structure, no cleavage, high specific gravity.

Identified October 18, 2026More sedimentary →

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Physical properties

Hardness 6-7 on the Mohs scale, grey to brown color, dull luster, amorphous or cryptocrystalline structure, no cleavage, high specific gravity.

Formed through the precipitation of mineral cement within the pores of sandstone sediments, often originating in Cretaceous marine environments.

Primarily valued as unique natural geological specimens by collectors and used as decorative landscaping ornaments.

These spherical structures often weather out of softer surrounding sedimentary cliffs, famously found along the Cannonball River in North Dakota.

Easily identified by their remarkably spherical shape and weathering patterns; found worldwide in sedimentary rock formations.

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

Fossiliferous Sedimentary Rock

Sedimentary limestone with invertebrate fossil imprint

Sandstone or Siltstone

Arenite (if sandstone)

Sandstone

Arenite

Shale

Shale (clastic sedimentary rock)

Shale (or Mudstone/Siltstone)

Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)