fossil

Fossilized ammonite

Ammonoidea (likely a small, chambered ammonite fossil)

AI-generated identification · may be incorrect

A coiled, planispiral shell with visible chambers and ribbing, preserved in cream-to-brown mineralized material. Original shell aragonite is commonly replaced by calcite; hardness is typically about 3–4, with dull to slightly waxy luster and no reliable cleavage.

Identified September 8, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites were extinct marine cephalopods that lived from the Devonian through the Cretaceous, becoming extinct about 66 million years ago. Their shells accumulated in marine sediments and were later buried, lithified, and mineralized during diagenesis.

Uses & applications

Primarily used for education, paleontological study, décor, and collecting; polished ammonites are sometimes sold as jewelry or ornaments. Value depends heavily on size, preservation, locality, and preparation.

Geological facts

The spiral is divided into chambers that controlled buoyancy, while the animal occupied the youngest outer chamber. The pictured specimen appears naturally weathered or partially prepared, with strong ribs and exposed internal chambers.

Field identification & locations

Identify it by its symmetric spiral shell, repeated chamber partitions, and radial ribs; it is not a rock type in the strict sense but a fossilized biological structure. Common sources include Morocco, Madagascar, the United Kingdom, Germany, and Canada.