Rock Identifier

fossil

Echinoid Fossil

Class Echinoidea

AI-generated identification · may be incorrect

Hardness 3 on Mohs scale, calcium carbonate composition, typically featuring a spherical or flattened test with pentameral symmetry and spine tubercles.

Identified November 9, 2026More fossil →

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Physical properties

Hardness 3 on Mohs scale, calcium carbonate composition, typically featuring a spherical or flattened test with pentameral symmetry and spine tubercles.

Formation & geological history

Formed through the fossilization of marine invertebrates, where calcareous skeletal plates are replaced or infilled by minerals like calcite or silica over millions of years.

Uses & applications

Valued as a paleontology specimen, educational tool, and decorative collectible.

Geological facts

Echinoids have a fossil record stretching back over 450 million years to the Ordovician period.

Field identification & locations

Identified by radial symmetry and ornate plate patterns; commonly found in marine sedimentary limestone and chalk deposits globally.

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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) — fossil

Likely fossil oyster shell

Fossilized bivalve shell; exact species cannot be identified from the image

Crinoid Stem Fossil in Matrix (Phylum Echinodermata, Class Crinoidea) — fossil

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)) — sedimentary

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) — sedimentary

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)) — fossil

Fossil oyster shell

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