fossil

Fossil brachiopod or bivalve shell

Indeterminate fossilized carbonate shell; likely a brachiopod (Phylum Brachiopoda)

AI-generated identification · may be incorrect

Pale gray-beige, weathered, and compact with faint growth/radial ridges; likely calcite or recrystallized calcium carbonate. Calcite has Mohs hardness 3, vitreous to dull luster, rhombohedral cleavage, and specific gravity about 2.7; exact properties are obscured by preservation.

Identified August 15, 2026More fossil →

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Physical properties

Formation & geological history

A marine shell was buried in carbonate sediment and mineralized or recrystallized during diagenesis, probably during the Paleozoic or Mesozoic; age cannot be determined from the image. Brachiopods are commonly preserved as isolated valves in limestone and shale.

Uses & applications

Primarily a collecting, educational, or decorative specimen; fossil carbonate material has little industrial value unless part of a larger limestone deposit.

Geological facts

The asymmetric, rounded form and possible central ridge favor a brachiopod, while bivalves usually have two more-symmetrical matching valves. Surface wear makes a definitive identification difficult.

Field identification & locations

Look for bilateral symmetry, a hinge line, radial ribs, and a beak or umbo; a dilute acid test may fizz if exposed calcite is present. Common in marine sedimentary rocks worldwide, especially Paleozoic formations.