fossil

Fossil Coral

Rugosa / Hexagonaria (CaCO3)

Mohs hardness 3-4; typically white, grey, or tan; dull to vitreous luster; hexagonal crystal structure of calcite.

Identified October 27, 2026More fossil →

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Physical properties

Mohs hardness 3-4; typically white, grey, or tan; dull to vitreous luster; hexagonal crystal structure of calcite.

Formed through the fossilization of ancient marine coral skeletons preserved in sedimentary limestone over millions of years.

Used in ornamental carvings, jewelry making, and as a popular specimen for fossil collectors.

Petoskey stone is a well-known fossil coral and the official state stone of Michigan, featuring distinct star-like corallites.

Identified by distinctive daisy or honeycomb-like patterns on the surface; found worldwide in ancient marine sedimentary deposits.

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