Rock Identifier
Fossil Bivalve (Class Bivalvia) — fossil
fossil

Fossil Bivalve

Class Bivalvia

AI-generated identification · may be incorrect

Hardness 3-4 (calcite/aragonite), gray to dark brown color, pearly to dull luster, orthorhombic/trigonal crystal system, specific gravity 2.7.

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Physical properties

Hardness 3-4 (calcite/aragonite), gray to dark brown color, pearly to dull luster, orthorhombic/trigonal crystal system, specific gravity 2.7.

Formation & geological history

Formed through permineralization or replacement in marine sedimentary environments, often dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used primarily in paleontological research, educational displays, and fossil collecting.

Geological facts

Bivalves first appeared over 500 million years ago and include clams, oysters, and mussels. Their fossilized remains are exceptional index fossils for dating sedimentary rock layers.

Field identification & locations

Identify by distinct hinged two-valve shells with radial or concentric ribs, commonly found embedded in marine limestone, shale, or sandstone.

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Probable fossil-bearing rock or mineral concretion (Unidentified carbonate-rich concretion with a possible fossil inclusion) — fossil

Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

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Likely fossil oyster shell (Fossilized bivalve shell; exact species cannot be identified from the image) — fossil

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

fossil
Crinoid Stem Fossil in Matrix (Phylum Echinodermata, Class Crinoidea) — fossil

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil
Fossiliferous limestone (likely a crinoidal or shell-fragment limestone) (Bioclastic limestone, composed chiefly of calcite (CaCO₃)) — sedimentary

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

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

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

Porous limestone pebble

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

sedimentary
Weathered fossil bone fragment (identification uncertain) (Fossilized bone; exact taxon and mineral composition cannot be determined from the image) — fossil

Weathered fossil bone fragment (identification uncertain)

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

fossil