fossil

Rugose Coral Fossil

Order Rugosa

Hardness of 3-4 on the Mohs scale, typically brown, tan, or gray with a horn-like or cylindrical shape and calcite composition.

Identified October 31, 2026More fossil →

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Physical properties

Hardness of 3-4 on the Mohs scale, typically brown, tan, or gray with a horn-like or cylindrical shape and calcite composition.

Formed during the Paleozoic era, roughly 250 to 500 million years ago, as solitary marine organisms secreted calcium carbonate skeletons.

Used primarily by fossil collectors, educational displays, and in biostratigraphy to date rock layers.

Also known as horn corals, these organisms went extinct during the Permian-Triassic extinction event.

Identify by its distinct horn-like curved shape and radial internal septa; commonly found in Paleozoic limestone and shale deposits worldwide.

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