fossil

Fossil Coral (Tabulate Coral Fragment)

Anthopleura / Tabulata (CaCO3 - Calcium Carbonate)

Hardness: 3-3.5 on the Mohs scale (calcite) or up to 6.5-7 if silicified. Color: Beige, light tan, brownish, or pale orange. Luster: Dull to earthy, vitreous if replaced by quartz. Structure: Distinct internal mesh or honeycomb structure (corallites).

Hardness: 3-3
Color: Beige, light tan, brownish, or pale orange
Luster: Dull to earthy, vitreous if replaced by quartz

Identified July 26, 2026More fossil →

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Physical properties

Formation & geological history

Formed during the Paleozoic Era (Ordovician to Permian) in warm, shallow marine environments. Over millions of years, the calcium carbonate skeleton of colonial coral was buried by sediment and fossilized or replaced with silica/calcite.

Uses & applications

Used as educational geological specimens, in fossil collections, polished for lapidary work and jewelry, and historically as a limestone component in construction.

Geological facts

Tabulate corals are an extinct order of coral that were major reef builders during the Silurian and Devonian periods. They went completely extinct during the Permian-Triassic extinction event around 252 million years ago.

Field identification & locations

Identified in the field by the distinct cross-hatched, grid-like, or honeycomb structure (corallite walls and tabulae) visible on weathered surfaces. Commonly found along ancient sea beds, limestone quarries, and gravel bars in rivers.

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