fossil

Polished fossilized ammonite or nautiloid shell

Ammonoidea or Nautiloidea; originally aragonitic shell, commonly replaced by calcite or chalcedony

AI-generated identification · may be incorrect

Dark, highly polished, flattened discoidal specimen with a visible central suture or chamber line; hardness typically 3.5–7 depending on mineral replacement, vitreous to waxy luster, and curved septa/chambers. The broad outline and internal segmentation are consistent with a fossil cephalopod shell.

Identified August 10, 2026More fossil →

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Physical properties

Formation & geological history

A marine cephalopod shell was buried in sediment and fossilized through mineral replacement and compaction, commonly during the Paleozoic or Mesozoic eras (about 485–66 million years ago). It has been cut and polished for display.

Uses & applications

Used as a decorative fossil, educational specimen, and collector display; uncommon large polished examples may be sold as art objects.

Geological facts

Ammonites show characteristic chamber partitions and sutures, while nautiloids usually have simpler sutures; the image’s dark polish obscures decisive details. Many commercial specimens are sourced from Morocco, Madagascar, Pakistan, and Europe.

Field identification & locations

Inspect the edge and unpolished areas for chambers, septa, and fossil shell texture; confirm with locality or seller documentation because polished black stone can also imitate fossils. Estimated value: $50–$500, or roughly $500–$2,000+ for a large, well-preserved authenticated specimen.