fossil

Pyritized Ammonite

Ammonoidea (replaced with FeS2)

Mohs hardness 6 to 6.5, metallic brassy to copper color, metallic luster, orthorhombic crystal system for the pyrite replacement.

Identified October 27, 2026More fossil →

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Physical properties

Mohs hardness 6 to 6.5, metallic brassy to copper color, metallic luster, orthorhombic crystal system for the pyrite replacement.

Formed during the Mesozoic era when ancient cephalopod shells were buried in oxygen-poor marine sediments and replaced by iron pyrite.

Prized by fossil and mineral collectors for display and educational purposes.

Commonly referred to as 'peacock ore' or pyrite fossils, these specimens exhibit a brilliant natural metallic iridescence when well-preserved.

Found extensively in marine sedimentary formations such as the Volga River region in Russia and the Blue Lias in England.

Probable fossil-bearing rock or mineral concretion

Unidentified carbonate-rich concretion with a possible fossil inclusion

Likely fossil oyster shell

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

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

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

Bioclastic limestone, composed chiefly of calcite (CaCO₃)

Porous limestone pebble

Calcite-rich limestone (primarily CaCO₃); exact identification is uncertain from the image

Weathered fossil bone fragment (identification uncertain)

Fossilized bone; exact taxon and mineral composition cannot be determined from the image