fossil

Fossil ammonite fragment

Ammonoidea (likely a small heteromorph or coiled ammonite; exact genus indeterminate)

AI-generated identification · may be incorrect

A chambered, coiled shell fossil with visible septa and weathered porous limestone/matrix. Original shell was aragonite or calcite; hardness is typically about 3–4 where calcitic, with dull to earthy luster and no reliable cleavage.

Identified September 4, 2026More fossil →

Explore Fossil ammonite fragment in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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. The shell was buried in marine sediment and mineralized or replaced during diagenesis.

Uses & applications

Primarily a collectible, teaching specimen, or decorative fossil; small examples generally have little commercial use.

Geological facts

The internal partitions divided the shell into buoyancy chambers, while the animal occupied the outermost chamber. The visible spiral and septal pattern are key ammonite features.

Field identification & locations

Common fossil-bearing rocks include Jurassic and Cretaceous marine limestones and shales worldwide, especially in Morocco, Madagascar, Europe, and North America. Check for a continuous spiral, repeated chambers, and mineralized shell rather than a manufactured imprint.