fossil

Fossilized Bivalve Shell

Bivalvia (Phylum Mollusca)

Mohs hardness: 3.5 to 4 (calcite/aragonite); Color: Varies, typically brown, grey, or white with patterned exterior; Luster: Pearly to dull; Crystal structure: Orthorhombic or trigonal (mineral replacement); Cleavage: None; Specific Gravity: 2.7 to 2.9

Hardness: 3
Luster: Pearly to dull

Identified July 30, 2026More fossil →

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Physical properties

Formation & geological history

Formed through the process of permineralization or replacement where organic shell material is slowly substituted by minerals like silica, calcite, or pyrite over millions of years, typically dating from the Paleozoic to Cenozoic eras.

Uses & applications

Educational, paleontological study, decorative display, and fossil collecting.

Geological facts

Bivalves first appeared in the Cambrian period over 500 million years ago and are among the most common fossils found worldwide, providing critical data for paleoenvironmental reconstructions.

Field identification & locations

Easily identified by their symmetrical paired valves and characteristic radial ribs or growth lines. Commonly found in sedimentary rock formations such as limestone, shales, and sandstones near ancient marine environments.