fossil

Horn Coral Fossil

Rugose coral (Order Rugosa)

Hardness: 3-4 (calcite), Color: Grey, white, or brown, Luster: Dull to vitreous, Crystal structure: Hexagonal (calcite replacement), Cleavage: None (fractures), Specific gravity: 2.7

Identified August 2, 2026More fossil →

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Physical properties

Hardness: 3-4 (calcite), Color: Grey, white, or brown, Luster: Dull to vitreous, Crystal structure: Hexagonal (calcite replacement), Cleavage: None (fractures), Specific gravity: 2.7

Formation & geological history

Formed through the fossilization of solitary rugose corals that lived in shallow Paleozoic marine environments, predominantly during the Ordovician to Permian periods (approx. 450 to 250 million years ago), where their soft tissues were replaced by minerals like silica or calcite over millions of years.

Uses & applications

Used primarily in educational displays, fossil collecting, and occasionally crafted into unique jewelry pieces.

Geological facts

Rugose corals are commonly called horn corals because of their distinctive horn-like, curved shape resembling a ram's horn. They were solitary or colonial marine animals that became extinct during the Permian-Triassic extinction event.

Field identification & locations

Can be identified by their distinctive conical shape and prominent radial septa visible on the calice or outer surface. Commonly found in limestone deposits worldwide, especially in areas that were once ancient shallow seas.