fossil

Echinoid Fossil

Echinoidea class

Hardness 3 on Mohs scale (calcite replacement), brown to tan coloration, dull to vitreous luster, radial symmetry, specific gravity around 2.7.

Identified November 13, 2026More fossil →

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Physical properties

Hardness 3 on Mohs scale (calcite replacement), brown to tan coloration, dull to vitreous luster, radial symmetry, specific gravity around 2.7.

Formed in ancient shallow marine environments during the Paleozoic to Cenozoic eras when sea urchin shells were buried in sediment and mineralized.

Valued as a collector specimen, educational tool in paleontology, and occasionally used in jewelry or decorative displays.

Commonly known as sea urchin fossils or fairy loafs, they often show distinct five-fold symmetry on their test.

Found worldwide in limestone, chalk, and marine sedimentary deposits. Identify by their rounded, button-like shape and patterned plate structure.

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