fossil

Fossil coral limestone

Fossilized colonial coral, commonly Favosites or related tabulate coral, preserved in calcite (CaCO₃)

AI-generated identification · may be incorrect

Cream to pale tan, fine-grained and dull to softly waxy; Mohs hardness about 3, with calcite cleavage and specific gravity near 2.7. Repeated corallite/cell patterns are visible across the weathered surface.

Identified September 7, 2026More fossil →

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Physical properties

Formation & geological history

A Paleozoic marine coral colony was buried in carbonate sediment, then its original aragonite or calcitic skeleton was mineral-replaced and lithified into limestone, typically roughly 250–450 million years old.

Uses & applications

Collected as a fossil, educational specimen, and decorative stone; larger pieces may be polished for display, though it has limited industrial value compared with ordinary limestone.

Geological facts

The honeycomb-like pattern records individual coral animals (corallites) living in a shallow ancient sea; exact genus identification requires clearer views of the cell walls and internal structure.

Field identification & locations

Identify by the regular geometric coralites, relatively low hardness, and vigorous fizz with dilute hydrochloric acid or vinegar (test inconspicuously). Common in Paleozoic limestone deposits worldwide, including the Great Lakes region and parts of Europe and Australia.