sedimentary

Rugose Coral (Horn Coral)

Order Rugosa (extinct fossilized coral)

AI-generated identification · may be incorrect

Hardness: 3-4 (calcite); Color: Tan, brown, or orange due to mineral staining; Luster: Dull to earthy; Shape: Characteristic conical, horn-like shape with septa (ridges) inside the cup.

Hardness: 3-4 (calcite)
Color: Tan, brown, or orange due to mineral staining
Luster: Dull to earthy

Identified April 12, 2026More sedimentary →

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Physical properties

Hardness: 3-4 (calcite); Color: Tan, brown, or orange due to mineral staining; Luster: Dull to earthy; Shape: Characteristic conical, horn-like shape with septa (ridges) inside the cup.

Formation & geological history

Formed as the calcium carbonate skeleton of a solitary marine polyp. Most common specimens date from the Ordovician to the Permian periods (approx. 488 to 251 million years ago). They lived on the seafloor in ancient tropical seas.

Uses & applications

Primarily used for geological education, fossil collecting, and occasionally as decorative pieces or jewelry components when polished.

Geological facts

Horn corals are extinct; they disappeared during the Great Permian Extinction. Unlike modern corals, many were solitary individuals rather than part of a colonial reef.

Field identification & locations

Identify by its curved, conical shape resembling a bull's horn and the radial symmetry visible in the cross-section of the 'top' or cup. Found globally in limestone and shale deposits.