fossil

Fossil bivalve shell

Fossilized mollusk (Bivalvia), likely an oyster or clam; exact genus requires locality and diagnostic features

AI-generated identification · may be incorrect

A rounded, asymmetric shell with prominent growth lines and a thick, pale calcitic exterior; the dark gray area may be sediment, mineral replacement, or matrix. Original shell is mostly calcium carbonate (calcite/aragonite), Mohs hardness about 3–4, with dull to pearly luster and no visible crystal cleavage.

Identified August 19, 2026More fossil →

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Physical properties

Formation & geological history

Formed when a marine bivalve was buried in sediment and its shell was preserved, sometimes with partial mineral replacement. Age cannot be determined from the image; comparable specimens range from Paleozoic to modern-appearing fossil deposits.

Uses & applications

Primarily a collecting, educational, and decorative specimen; fossil shells are occasionally used in geology displays and lapidary work but have little industrial value.

Geological facts

The shell’s hinge, ribs, and growth pattern are key for identification, but the visible specimen appears weathered and partly matrix-filled.

Field identification & locations

Common in marine limestone, coastal sedimentary rocks, and fossil beds worldwide; inspect the hinge and interior valve, and test cautiously for calcite reaction with dilute acid. Typical value is $5–$30, or about $30–$100 for an attractive, well-prepared, locality-documented specimen.