fossil

Fossilized ammonite (likely weathered ammonite cross-section)

Ammonoidea; commonly Jurassic–Cretaceous ammonite fossils replaced by calcite or aragonite

AI-generated identification · may be incorrect

Hardness about 3–4 (calcite-replaced material), pale gray-brown to cream, dull to waxy luster, and strongly coiled chambered structure; visible sutures and shell whorls are diagnostic. The specimen appears weathered and possibly polished or coated.

Identified August 10, 2026More fossil →

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At a glance

Common name: Fossilized ammonite (likely weathered ammonite cross-section)
Scientific name: Ammonoidea; commonly Jurassic–Cretaceous ammonite fossils replaced by calcite or aragonite
Category: fossil
Identified: August 10, 2026
Method: Standard

AI Estimated Value

Approximately $20–$150 for a common weathered specimen; $200–$1,000+ for large, complete, well-prepared or iridescent examples.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Ammonites were marine cephalopods that lived from the Devonian to the end-Cretaceous extinction (~409–66 million years ago). Their shells were buried in marine sediment and later mineralized, commonly by calcite, during diagenesis.

Uses & applications

Collected as a fossil and used for educational displays, decorative objects, and jewelry when cut or polished. Value depends heavily on preservation, identifiable suture patterns, size, and provenance.

Geological facts

The apparent spiral chambers and radiating internal partitions distinguish it from an ordinary rock; some ammonites preserve iridescent nacre, called ammolite, especially from Alberta, Canada.

Field identification & locations

Common sources include Morocco, Madagascar, Germany, the United Kingdom, Russia, and western North America. Confirm by looking for a continuous logarithmic coil, repeated chambers, and septal sutures; a field hardness test should be avoided on valuable specimens.