fossil

Rugose Coral Fossil

Order Rugosa

Hardness varies around 3 to 4 (calcite), color typically brownish-grey to black for the fossilized coral embedded in a lighter limestone matrix, vitreous to dull luster, horn-shaped or cylindrical corallite structure.

Identified July 29, 2026More fossil →

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Physical properties

Formation & geological history

Formed in ancient shallow marine environments during the Paleozoic era (ranging from the Ordovician to the Permian period, approximately 488 to 251 million years ago), where coral skeletons were rapidly buried in sediment and mineralized.

Uses & applications

Used primarily in fossil collecting, educational displays, and as index fossils to help date geological strata.

Geological facts

Rugose corals are commonly known as horn corals because of their unique horn-like shape. They are extinct marine invertebrates that lived hundreds of millions of years ago.

Field identification & locations

Found embedded in limestone and sedimentary rock formations worldwide, particularly in regions that were once covered by ancient shallow seas. Collectors look for distinct radial symmetry and the characteristic horn-like shape protruding from the rock matrix.