fossil

Fossil brachiopod or bivalve shell

Indeterminate fossilized carbonate shell; possibly a brachiopod (Brachiopoda)

AI-generated identification · may be incorrect

Cream-gray, weathered, low-luster shell with strong radial ribs and bilateral-looking symmetry; composed mainly of fossilized calcite or aragonite. Calcite hardness is about 3 Mohs, with moderate density and possible weak cleavage.

Identified August 17, 2026More fossil →

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Physical properties

Formation & geological history

A marine shell was buried in sediment and mineralized during diagenesis, commonly in Paleozoic–Mesozoic carbonate rocks. The exact age and identity require examining the hinge, symmetry, and internal features.

Uses & applications

Primarily a teaching, collecting, and display specimen; it has no significant industrial or jewelry use. Small common fossils generally have modest commercial value.

Geological facts

Radial ribbing is characteristic of many brachiopods and bivalves, but brachiopods are typically symmetric through each valve while bivalves are symmetric across the hinge. The visible specimen may be a partial or worn shell.

Field identification & locations

Common in marine limestone and shale worldwide, especially Paleozoic formations. Test suspected calcite with dilute acid for fizzing, inspect for preserved hinge structures, and avoid confusing it with a modern shell or cast.