fossil

Fossil ammonite fragment

Ammonoidea (likely a Jurassic–Cretaceous ammonite)

AI-generated identification · may be incorrect

Fossilized coiled cephalopod shell with visible chamber/septum structures; typically calcite or aragonite replaced by calcite, Mohs hardness about 3–4, dull to subvitreous luster, and curved ribbing. The dark coloration likely reflects mineral staining or carbonaceous material.

Identified August 25, 2026More fossil →

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Physical properties

Formation & geological history

Ammonites lived in marine environments and formed chambered aragonitic shells; after burial, the shell was mineralized and partially weathered. Most commercial examples are Mesozoic, roughly 201–66 million years old.

Uses & applications

Primarily a collector, educational, and decorative specimen; polished ammonites may be used in jewelry and ornamentation, but this small fragment has limited commercial utility.

Geological facts

Ammonites are extinct relatives of modern nautiluses and cuttlefish, not modern shelled snails. Their chambered shells are valuable index fossils for correlating Mesozoic marine rocks.

Field identification & locations

Identify by a planispiral coil, repeated chambers, septa, and ribs; common sources include Madagascar, Morocco, the United Kingdom, Germany, and Alberta. Avoid acid testing if preservation is important, since calcite dissolves in acid.