fossil

Echinoid Fossil

Echinoidea class

Hardness 3 on Mohs scale (calcite), reddish-brown color, dull to vitreous luster, radial symmetry, specific gravity 2.7.

Identified November 7, 2026More fossil →

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Physical properties

Hardness 3 on Mohs scale (calcite), reddish-brown color, dull to vitreous luster, radial symmetry, specific gravity 2.7.

Formed during the Mesozoic to Cenozoic eras when marine invertebrate remains were buried in sediment and mineralized.

Used primarily for educational display, fossil collecting, and paleoecological research.

Commonly known as sea urchin fossils or prehistoric 'fairy loaves', they often weather out of limestone and chalk formations.

Identify by their distinct five-fold radial symmetry and rounded, button-like shape; found globally in ancient marine sedimentary strata.

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)