fossil

Fossilized Echinoid

Echinoidea

Hardness 3-4 (calcite), color varies from grey to tan, dull to vitreous luster, radial symmetry visible in test structure.

Identified November 7, 2026More fossil →

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Physical properties

Hardness 3-4 (calcite), color varies from grey to tan, dull to vitreous luster, radial symmetry visible in test structure.

Formed in marine sedimentary environments worldwide during the Paleozoic to Cenozoic eras through the mineralization of sea urchin shells.

Used primarily in paleontology, educational displays, and as a popular collectible specimen.

Commonly known as sea urchin fossils or fairy loafs, they often exhibit preserved pentameral symmetry on the fossilized test.

Identify by their distinct rounded or heart shape and five-rayed star patterns on the surface; found in limestone and chalk deposits globally.

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)