fossil

Fossilized coral (likely tabulate or colonial coral)

Fossil coral; possibly Hexagonaria or related Paleozoic colonial coral

AI-generated identification · may be incorrect

Identified September 12, 2026More fossil →

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Physical properties

Silicified or calcitic coral with tightly packed corallite pits, gray-brown color, dull to slightly waxy luster, and no obvious cleavage; hardness commonly 3–7 depending on whether calcite or silica replaced the original skeleton. The elongated, weathered form and repeated holes are diagnostic of coral structure rather than vesicular volcanic rock.

Formation & geological history

A marine colonial coral skeleton was buried in carbonate sediment and later preserved by calcite or silica mineralization, commonly during the Paleozoic Era (about 541–252 million years ago). Erosion exposed and rounded the specimen.

Uses & applications

Collected as a fossil, used for educational displays, cabochons, carvings, and polished decorative objects; gem-quality fossil coral can be jewelry material.

Geological facts

Fossil coral preserves the individual chambers or corallites of the original colony; the holes are biological structures, not gas bubbles. Exact identification requires a close-up of the pit geometry or a thin section.

Field identification & locations

Common in ancient limestone deposits, including parts of the Great Lakes region, Australia, Morocco, and the western United States. Look for repeating polygonal or circular corallites arranged in colonies; acid testing can distinguish calcitic coral from silicified material.