Rock Identifier
Fossil shell fragment (likely brachiopod or bivalve) (Indeterminate fossilized carbonate shell; likely Brachiopoda or Bivalvia) — fossil
fossil

Fossil shell fragment (likely brachiopod or bivalve)

Indeterminate fossilized carbonate shell; likely Brachiopoda or Bivalvia

AI-generated identification · may be incorrect

Dark brown to black, elongated curved form with a hard, slightly glossy surface and apparent shell growth texture. Original calcite or aragonite shell has likely been replaced or stained by iron/manganese minerals; hardness commonly ~3–4, with no visible crystal structure.

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Physical properties

Dark brown to black, elongated curved form with a hard, slightly glossy surface and apparent shell growth texture. Original calcite or aragonite shell has likely been replaced or stained by iron/manganese minerals; hardness commonly ~3–4, with no visible crystal structure.

Formation & geological history

A marine shell buried in carbonate-rich sediment and fossilized through mineral replacement or cementation, probably Paleozoic–Cenozoic in age. Exact age and identity require locality and microscopy.

Uses & applications

Primarily a teaching or collecting specimen; not typically used industrially, ornamentally, or as jewelry unless polished.

Geological facts

The curved profile and parallel surface ridges resemble a fossil shell valve or shell fragment, but the image is insufficient for species-level identification.

Field identification & locations

Confirm it is geological by testing whether it is stone-hard and non-flexible; a dilute acid reaction may indicate carbonate, though replacement can suppress effervescence. Common in marine limestone, shale, and fossil beds worldwide.

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Fossiliferous limestone (likely a crinoidal or shell-fragment limestone)

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

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Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image

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Weathered fossil bone fragment (identification uncertain)

Fossilized bone; exact taxon and mineral composition cannot be determined from the image

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