fossil

Fossilized Rugose Coral (Horn Coral)

Order Rugosa

Hardness: 3-4 (Calcite composition). Color: Tan, grey, or white. Luster: Dull/earthy. Structure: Solitary horn-like shape with radial septa radiating from a central point.

Hardness: 3-4 (Calcite composition)
Color: Tan, grey, or white
Luster: Dull/earthy

Identified July 8, 2026More fossil →

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Physical properties

Hardness: 3-4 (Calcite composition). Color: Tan, grey, or white. Luster: Dull/earthy. Structure: Solitary horn-like shape with radial septa radiating from a central point.

Formation & geological history

Formed in shallow marine environments during the Paleozoic Era (Ordovician to Permian periods), approximately 488 to 251 million years ago.

Uses & applications

Used primarily for geological study, educational specimens, and as a collector's item for fossil enthusiasts.

Geological facts

Rugose corals are often called 'Horn Corals' because of their distinctive curved shape. They went extinct at the end of the Permian period during the 'Great Dying' mass extinction event.

Field identification & locations

Identified by the cone-like shape and visible ribs or septa inside the cup. Commonly found in limestone beds across the Midwestern United States and Europe.