Fossil

Bivalve Fossil

Bivalvia (Phylum Mollusca)

AI-generated identification · may be incorrect

Hardness varies based on replacement mineral (often calcite or quartz, 3-7 on Mohs scale). Color is typically grey, brown, or tan, reflecting the surrounding sedimentary rock. Exhibits distinct growth lines and a curved, asymmetrical shell shape.

Identified August 12, 2026More fossil →

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Physical properties

Formation & geological history

Formed in marine or freshwater environments when a bivalve mollusk died and was buried in sediment. Over time, minerals replaced the original shell material (permineralization) or the shell dissolved leaving a cast or mold.

Uses & applications

Used primarily for paleontological study, biostratigraphy (dating rock layers), and collecting. Occasionally used in jewelry if the fossilization involves attractive minerals like opal or pyrite.

Geological facts

Bivalve fossils are extremely common and can be found in sedimentary rocks worldwide. They first appeared in the Cambrian period, over 500 million years ago.

Field identification & locations

Identified by their two-valved shell structure, often with a hinge line and growth rings. Commonly found in limestone, shale, and sandstone deposits. Collectors look for complete, well-preserved shells or interesting internal molds.