Fossilized Bivalve Shell

Physical Properties

Hardness: 3-3.5 (Calcite); Color: Off-white, grey, or tan; Luster: Dull to chalky; Structure: Concentric growth lines; Composition: Calcium carbonate (Calcite/Aragonite).

Formation & Geological History

Formed when a marine or freshwater mollusk was buried in sediment. Over time, mineral replacement or permineralization occurs. These can date from the Paleozoic to the Holocene.

Uses & Applications

Paleontological study, educational tools, decorative items, and amateur fossil collecting.

Geological Facts

The tiny holes visible on the surface are likely bioerosion marks caused by boring organisms like sponges (Cliona) or predatory gastropods after the mollusk died.

Field Identification & Locations

Identified by symmetrical valves and visible growth rings. Commonly found in limestone outcrops, riverbeds, and coastal sedimentary formations.

Identified on: 5/10/2026

Mode: Standard