fossil

Fossil brachiopod or bivalve shell

Likely a fossilized brachiopod; precise genus cannot be determined from the photograph

AI-generated identification · may be incorrect

Calcareous shell replaced or reinforced by mineralized carbonate; gray-tan, dull to slightly waxy luster, ribbed/ornamented surface, and a central commissure or seam. Calcite shell material is Mohs hardness about 3 and reacts with dilute hydrochloric acid.

Identified August 13, 2026More fossil →

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Physical properties

Formation & geological history

Formed when a marine shell was buried in sediment and mineralized during diagenesis, commonly in Paleozoic–Mesozoic marine limestone. The visible symmetry and longitudinal ribs are more suggestive of a brachiopod than an ordinary rock.

Uses & applications

Primarily a collecting, educational, and decorative specimen; fossiliferous limestone may also be used as aggregate or building stone, but this individual has little industrial value.

Geological facts

Brachiopods resemble clams but have bilateral symmetry through each valve rather than between the two valves. Many species lived attached to the seafloor by a fleshy stalk.

Field identification & locations

Look for a paired shell, radiating ribs, a hinge area, and carbonate reaction; compare both valves and inspect the underside for hinge structures. Common in sedimentary rocks worldwide, especially Paleozoic formations.