sedimentary
Cannonball Concretion
Calcite-cemented Sandstone Concretion
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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