Rock Identifier
Fossil ammonite (Ammonite (subclass Ammonoidea; exact species not identifiable from the image)) — fossil
fossil

Fossil ammonite

Ammonite (subclass Ammonoidea; exact species not identifiable from the image)

AI-generated identification · may be incorrect

A coiled, chambered shell fossil, cream to tan with a rough, weathered surface. The original shell is commonly replaced by calcite or other minerals; hardness depends on the preservation and host material.

Identified More fossil →
Explore Fossil ammonite in the encyclopedia →

Identify your own rocks.

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

App StoreGoogle Play

Physical properties

A coiled, chambered shell fossil, cream to tan with a rough, weathered surface. The original shell is commonly replaced by calcite or other minerals; hardness depends on the preservation and host material.

Formation & geological history

Ammonites were marine cephalopods that lived from the Devonian to the end of the Cretaceous, about 400–66 million years ago. Their shells were buried in marine sediment and fossilized through mineral replacement or infilling.

Uses & applications

Collected and displayed as a fossil; polished ammonites are also used in jewelry and ornamental objects.

Geological facts

The visible spiral reflects the animal’s planispirally coiled shell, which was divided into buoyancy-regulating chambers.

Field identification & locations

Look for the characteristic coiled shell and, on better-preserved specimens, chamber divisions or ribbing. Ammonites occur in sedimentary rocks worldwide; the pictured specimen’s exact locality and species cannot be determined from the image.

More like this

Other fossil specimens

Probable fossil-bearing rock or mineral concretion (Unidentified carbonate-rich concretion with a possible fossil inclusion) — fossil

Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

fossil
Likely fossil oyster shell (Fossilized bivalve shell; exact species cannot be identified from the image) — fossil

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

fossil
Crinoid Stem Fossil in Matrix (Phylum Echinodermata, Class Crinoidea) — fossil

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil
Fossiliferous limestone (likely a crinoidal or shell-fragment limestone) (Bioclastic limestone, composed chiefly of calcite (CaCO₃)) — sedimentary

Fossiliferous limestone (likely a crinoidal or shell-fragment limestone)

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

sedimentary
Fossil oyster shell (Oyster (family Ostreidae); shell composed chiefly of calcite (CaCO₃)) — fossil

Fossil oyster shell

Oyster (family Ostreidae); shell composed chiefly of calcite (CaCO₃)

fossil
Rounded sedimentary pebble (Likely micritic limestone or calcareous sandstone) — sedimentary

Rounded sedimentary pebble

Likely micritic limestone or calcareous sandstone

sedimentary