Rock Identifier
Cannonball Concretion (Calcite-cemented Sandstone Concretion) — sedimentary
sedimentary

Cannonball Concretion

Calcite-cemented Sandstone Concretion

AI-generated identification · may be incorrect

Hardness of 6 to 7 on the Mohs scale (due to quartz sand and cement), color ranges from light grey to brown, dull luster, amorphous or granular crystal structure inside, no true cleavage, specific gravity around 2.6 to 2.7.

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Physical properties

Hardness of 6 to 7 on the Mohs scale (due to quartz sand and cement), color ranges from light grey to brown, dull luster, amorphous or granular crystal structure inside, no true cleavage, specific gravity around 2.6 to 2.7.

Formation & geological history

Formed in sedimentary basins through the precipitation of mineral cement (typically calcium carbonate) around a nucleus within sand or mud layers, often during the Cenozoic or Cretaceous periods.

Uses & applications

Mainly collected as geological curiosities, ornamental landscape stones, or educational specimens.

Geological facts

Often mistaken for fossilized dinosaur eggs or ancient cannonballs due to their remarkably spherical shape, famous examples are found at North Dakota's Cannonball River and New Zealand's Moeraki Boulders.

Field identification & locations

Identified by their distinct spherical or discoidal shapes weathering out of softer sedimentary host rock cliffs or riverbanks.

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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
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Sandstone (Arenite) — sedimentary

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