sedimentary

Rugose Coral Fossil

Rugosa (Order)

Hardness: 3 (calcite matrix), Color: Tan, beige, or grey, Luster: Dull/earthy to slightly vitreous, Structure: Radiating septa visible in cross-section, often shaped like a horn.

Identified June 12, 2026More sedimentary →

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Physical properties

Hardness: 3 (calcite matrix), Color: Tan, beige, or grey, Luster: Dull/earthy to slightly vitreous, Structure: Radiating septa visible in cross-section, often shaped like a horn.

Formation & geological history

Formed through the fossilization of marine organisms in shallow sea environments, primarily during the Paleozoic era (Ordovician to Permian periods, approx. 488 to 251 million years ago).

Uses & applications

Educational specimen, paleontological research, and decorative collector pieces.

Geological facts

Also known as Horn Corals because of their unique conical shape. They were solitary reef-builders that went extinct during the Great Permian Extinction 251 million years ago.

Field identification & locations

Identify by radiating vertical lines (septa) and a tapered, curved shape. Commonly found in limestone outcrops and riverbeds in the Midwest US and UK.