fossil

Fossil coral in limestone

Fossilized colonial coral, likely tabulate or favositid coral (CaCO₃), preserved in calcitic limestone

AI-generated identification · may be incorrect

Cream-gray, porous specimen with repeated polygonal corallite impressions and brown iron-oxide staining; calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and fizzes in dilute hydrochloric acid.

Identified September 15, 2026More fossil →

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Physical properties

Formation & geological history

A marine coral colony was buried and mineralized, commonly during Paleozoic or Mesozoic reef formation; original aragonite or calcite skeletons were preserved or replaced by calcite, then exposed by weathering.

Uses & applications

Primarily a teaching and collecting specimen; polished fossil coral is used decoratively, while fossil coral gemstones and cabochons are occasionally made from silicified material.

Geological facts

The honeycomb-like pattern records individual coral polyps, making the specimen a fossil rather than modern coral. Exact age and genus require locality and microscopic examination.

Field identification & locations

Identify by the regular corallite pattern, low hardness, and acid reaction; common in ancient marine limestone from regions including the Great Lakes, Texas, Florida, Australia, and parts of Europe. Avoid strong acids and abrasion.