fossil

Fossil coral fragment

Likely colonial scleractinian coral; calcite/aragonite (CaCO₃)

AI-generated identification · may be incorrect

Cream-to-tan, porous honeycomb texture with polygonal corallites; dull to slightly vitreous luster. Mohs hardness about 3–4; relatively light, with no obvious cleavage. The original aragonite may be recrystallized to calcite during fossilization.

Identified August 25, 2026More fossil →

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Physical properties

Formation & geological history

A colonial coral skeleton accumulated in a shallow tropical marine reef, commonly during the Paleozoic or Mesozoic; exact age and genus require locality and microscopic study. Burial, mineral replacement, and lithification preserved the corallite pattern.

Uses & applications

Primarily a collecting, educational, and decorative specimen; polished fossil coral is sometimes used in jewelry and ornamental objects. Avoid acids, which dissolve carbonate material.

Geological facts

The repeated cups or tubes are individual coral animals (corallites), not vesicles in volcanic rock. Pattern geometry can help distinguish rugose, tabulate, and scleractinian coral groups.

Field identification & locations

Identify by its consistent, biological honeycomb structure and carbonate reaction: a drop of dilute hydrochloric acid or vinegar may fizz, though testing can damage it. Fossil coral occurs in sedimentary limestone deposits worldwide, including Florida, the Great Lakes region, Australia, and Madagascar.