fossil

Bivalve Fossil (Clam)

Class Bivalvia (e.g., Mercenaria or similar genus)

Hardness: 3-4 (Calcite/Aragonite replacement), Color: Tan to grey, Luster: Dull/Earthy, Crystal Structure: Typically microcrystalline calcite replacement of original shell calcium carbonate, Shape: Symmetric valves with distinct hinge line.

Identified July 4, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization or recrystallization in marine or freshwater sedimentary environments. The soft tissue decays, leaving the shell to be buried by sediment and eventually lithified. Geological age ranges from the Cambrian to the present.

Uses & applications

Educational tools, paleontology study, hobbyist collecting, and sometimes used in decorative mosaics or jewelry if highly silicified.

Geological facts

Bivalves are one of the most successful groups of mollusks. Some fossilized clams can grow to massive sizes (like the Giant Clam), while others provide crucial data for dating sedimentary rock layers.

Field identification & locations

Identify by looking for bilateral symmetry between two shells (valves) and a visible hinge line (umbo). Commonly found in limestone, shale, or sandstone outcrops near ancient coastlines.

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Sedimentary bedrock formation (variable composition)

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Fossiliferous Limestone

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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Fossiliferous Limestone with Crinoid stems

Limestone (CaCO3) containing Crinoidea fossils

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