fossil

Polished ammonite fossil

Ammonoidea; likely a polished ammonite fragment, possibly an aptychus-associated piece

AI-generated identification · may be incorrect

Fossilized, chambered spiral shell with brown-gold calcite/aragonite coloration and polished luster; hardness typically about 3–4, with visible sutures and curved shell chambers. The specimen appears cut or tumbled rather than naturally weathered.

Identified August 29, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites were extinct marine cephalopods that lived from the Devonian to the end-Cretaceous, roughly 400–66 million years ago. Their aragonitic shells were commonly replaced or infilled by calcite, iron oxides, and other minerals during burial and diagenesis.

Uses & applications

Used mainly as a collectible, fossil display, jewelry component, or cabochon; it has little industrial value. Iridescent or exceptionally preserved examples can be valuable.

Geological facts

The chamber boundaries, called sutures, are characteristic of ammonites and helped regulate buoyancy. Brown coloration commonly results from iron staining or mineral replacement.

Field identification & locations

Identify it by the coiled geometry, repeated internal chambers, and ornate suture lines; common sources include Madagascar, Morocco, Alberta, and England. Avoid acids and prolonged soaking, which can damage calcitic or aragonitic surfaces.