fossil

Rugose Coral Fossil

Order Rugosa

Mohs hardness around 3 to 4, typically grayish or brownish white, vitreous to dull luster, horn-shaped solitary coral structure.

Identified November 7, 2026More fossil →

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

Physical properties

Mohs hardness around 3 to 4, typically grayish or brownish white, vitreous to dull luster, horn-shaped solitary coral structure.

Formed during the Paleozoic era (Ordovician to Permian) through permineralization of marine coral skeletons in shallow tropical seas.

Used for fossil collecting, educational displays, and occasionally lapidary cabochons.

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

Identify by distinctive horn shape and internal septal structures; commonly found in Paleozoic limestone 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

Fossil oyster shell

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