fossil

Fossilized ammonite

Ammonoidea (likely a heteromorph or heavily weathered ammonite); preservation may be calcitic replacement

AI-generated identification · may be incorrect

A coiled, ribbed cephalopod fossil with gray-beige coloration and dull to slightly waxy luster; original shell is commonly aragonite replaced by calcite or dissolved and infilled. Mohs hardness is typically about 3–4, with curved chamber sutures often visible.

Identified August 30, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites were marine cephalopods that lived from the Devonian to the end-Cretaceous, roughly Devonian–66 million years ago. Their shells were buried in marine sediment and later mineralized during diagenesis.

Uses & applications

Primarily collected, displayed, and used in paleontology and educational specimens; polished ammonites can be decorative. Value depends strongly on completeness, locality, preservation, and visible sutures.

Geological facts

The shell’s chambers were connected by a siphuncle and used for buoyancy control. The pictured specimen appears strongly weathered or partly eroded, making exact identification difficult.

Field identification & locations

Look for a planispiral coil, repeated ribs, chamber partitions, and branching or zigzag sutures; it is commonly found in Jurassic and Cretaceous marine limestones and shales. Typical value is about $10–$100, with exceptional complete specimens ranging from several hundred dollars upward.