fossil

Polished ammonite fossil

Ammonoidea; likely a Jurassic or Cretaceous ammonite, often sold as Cleoniceras or similar

AI-generated identification · may be incorrect

Fossilized, chambered spiral shell in limestone or aragonite/calcite replacement; brown, cream, and gray coloration, polished luster, hardness about 3–4, with visible septa and sutures. Ammonite shells have tightly coiled planispiral symmetry.

Identified August 27, 2026More fossil →

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Physical properties

Formation & geological history

Marine cephalopods that lived roughly Devonian–Cretaceous time (about 409–66 million years ago); the animal died, was buried in sediment, and its shell was mineral-replaced before cutting and polishing. Common commercial material comes from Madagascar and Morocco.

Uses & applications

Decorative objects, fossil collecting, educational displays, and jewelry; larger polished halves are commonly sold as display specimens.

Geological facts

The spiral chambers housed the ammonite’s soft body and helped regulate buoyancy. Complex suture patterns can help distinguish ammonite groups and estimate geological age.

Field identification & locations

Identify by the continuous spiral coil, repeated internal chambers, and branching sutures; unlike a nautiloid, ammonites generally show more elaborate sutures. Commonly found in sedimentary marine rocks in Madagascar, Morocco, England, Germany, and North America.