fossil

Fossilized shell fragment

Bioclastic carbonate, likely a bivalve or brachiopod shell preserved as calcite/aragonite

AI-generated identification · may be incorrect

Brown-gray, layered and strongly ribbed, with a dull to faintly pearly luster and irregular fracture. Original shell mineralogy is commonly calcite or aragonite; calcite hardness is Mohs 3, while aragonite is about 3.5–4, with visible growth lines and possible shell layers.

Identified September 13, 2026More fossil →

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Physical properties

Formation & geological history

A marine mollusk or brachiopod shell accumulated on the seafloor, was buried, and became mineralized or preserved in carbonate sediment. Its precise geological age cannot be determined from the photograph alone; such fossils range from Paleozoic to Recent deposits.

Uses & applications

Primarily a teaching, collecting, and lapidary specimen; polished fossil shell can be used decoratively, but it has little industrial value as an isolated fragment.

Geological facts

The concentric ridges are growth increments, and the dark color likely reflects mineral staining or replacement during burial. The broken interior may expose layered shell microstructure.

Field identification & locations

Identify it by repeated growth ribs, shell curvature, layered structure, and lack of uniform crystalline texture; dilute acid may effervesce if carbonate remains. Common in marine limestone, shale, and coastal deposits.