Rock Identifier
Fossilized echinoid (sea urchin), likely a sand dollar fragment or small regular urchin (Echinodermata; commonly Clypeasteroida or Echinoida, preserved mainly as calcite (CaCO₃)) — fossil
fossil

Fossilized echinoid (sea urchin), likely a sand dollar fragment or small regular urchin

Echinodermata; commonly Clypeasteroida or Echinoida, preserved mainly as calcite (CaCO₃)

AI-generated identification · may be incorrect

Hardness about 3 on Mohs scale; tan-beige, dull to slightly pearly luster, radial five-part symmetry, and porous calcitic structure. The central star-like petal pattern and radial grooves are characteristic of echinoid tests.

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Physical properties

Hardness about 3 on Mohs scale; tan-beige, dull to slightly pearly luster, radial five-part symmetry, and porous calcitic structure. The central star-like petal pattern and radial grooves are characteristic of echinoid tests.

Formation & geological history

A marine echinoid skeleton, originally aragonite/calcite, was buried in carbonate sediment and fossilized through mineral preservation and compaction. Exact age cannot be determined from the image; specimens range from Paleozoic to Recent deposits.

Uses & applications

Primarily a fossil-collecting and educational specimen; intact examples are used in natural-history displays and jewelry or décor. It has little industrial value.

Geological facts

Echinoid tests are made of many interlocking calcite plates, often producing a distinctive five-petal ambulacral pattern. The specimen appears worn or partially mineralized rather than a complete modern shell.

Field identification & locations

Look for fivefold symmetry, repeated plate divisions, and radial petal zones; limestone matrix or chalky texture supports identification. Common in shallow-marine limestones and coastal sediments worldwide, including Florida, England, Morocco, and the Gulf Coast.

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Phylum Echinodermata, Class Crinoidea

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Weathered fossil bone fragment (identification uncertain)

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