Rock Identifier
Bivalve Fossil (Class Bivalvia) — fossil
fossil

Bivalve Fossil

Class Bivalvia

AI-generated identification · may be incorrect

Hardness of 3-4 on the Mohs scale, typically grayish-brown to cream, dull to earthy luster, composed mainly of calcium carbonate in the form of calcite or aragonite.

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Physical properties

Hardness of 3-4 on the Mohs scale, typically grayish-brown to cream, dull to earthy luster, composed mainly of calcium carbonate in the form of calcite or aragonite.

Formation & geological history

Formed through permineralization or replacement where buried shells of marine organisms are slowly replaced by minerals in sedimentary layers over millions of years.

Uses & applications

Used in educational displays, fossil collecting, biostratigraphy, and decorative home decor.

Geological facts

Bivalves first appeared during the Cambrian period over 500 million years ago and are excellent index fossils for dating sedimentary strata.

Field identification & locations

Identify in the field by looking for symmetrical hinged shell impressions embedded in limestone, shale, or sandstone formations worldwide.

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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

fossil
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
Fossil oyster shell (Oyster (family Ostreidae); shell composed chiefly of calcite (CaCO₃)) — fossil

Fossil oyster shell

Oyster (family Ostreidae); shell composed chiefly of calcite (CaCO₃)

fossil