Fossil Shell in Sedimentary Matrix

Physical Properties

Hardness: 3-3.5 (Calcite); Color: creamy white to grey; Luster: dull to pearly; Structure: biogenic shell structure with surrounding grain texture; Cleavage: none (conchoidal or irregular fracture)

Formation & Geological History

Formed during the lithification of marine sediments where shellfish remains were buried and pressurized over millions of years, often in limestone or shale environments.

Uses & Applications

Educational specimens, decorative fossil displays, and used by collectors to study paleoenvironments. Fossiliferous limestone is also common in construction.

Geological Facts

Bivalve fossils can date back as far as the Cambrian period (over 500 million years ago) and help geologists determine the age and environment of rock layers.

Field Identification & Locations

Identify by the distinct symmetrical shell impressions or calcified remains embedded in softer rock; commonly found in riverbeds, cliffs, and quarries that were formerly ancient seabeds.

Identified on: 5/19/2026

Mode: Standard