fossil

Horn Coral Fossil

Order Rugosa

Hardness: 3-4 (retained by calcite/limestone replacement). Color: Gray, tan, or brown with possible iron staining. Features: Rugose (wrinkled) outer wall, conical or horn-shaped structure, interior radial septa/ribs.

Hardness: 3-4 (retained by calcite/limestone replacement)
Color: Gray, tan, or brown with possible iron staining

Identified July 4, 2026More fossil →

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Physical properties

Formation & geological history

Formed in shallow, warm marine environments during the Paleozoic Era (specifically Mississippian to Devonian periods in the Ohio River Valley region). These corals were solitary organisms that lived on the seafloor.

Uses & applications

Primarily for educational collections, research, and hobbyist fossil collecting. Larger or well-preserved specimens are used as decorative garden stones or paperweights.

Geological facts

Rugose corals were nicknamed 'Horn Corals' due to their resemblance to a cow's horn. They went extinct during the Great Permian Extinction approximately 250 million years ago and are unrelated to modern reef-building corals.

Field identification & locations

Found frequently in the limestone bedrock of the Louisville, Kentucky area (Falls of the Ohio). Look for wrinkled, funnel-shaped structures and radial lines in sedimentary outcroppings or creek beds.