fossil

Fossil Sea Urchin (Echinoid)

Echinoidea fossil (often replaced by silica or calcite)

Hardness varies from 3 to 7 depending on mineral replacement; color is typically grey, brown, or purplish due to weathering or mineral staining; dull to vitreous luster; internal radial symmetry with distinctive 5-petal ambulacral grooves.

Identified July 28, 2026More fossil →

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Physical properties

Formation & geological history

Formed when ancient sea urchins were buried rapidly in marine sediments (such as limestone, chalk, or flint-bearing formations) and their hard calcitic tests were fossilized and often mineralized over millions of years (commonly Cretaceous to Paleozoic eras).

Uses & applications

Valued by fossil collectors, used in educational displays, and sometimes made into jewelry or decorative items.

Geological facts

Often referred to locally as 'fairy loaves' or 'shepherd's stones' in folklore, fossilized sea urchins were historically placed on windowsills to ward off lightning or witchcraft.

Field identification & locations

Found worldwide in sedimentary marine deposits, particularly in chalk cliffs and limestone outcrops. Look for the distinct five-point star or petal pattern on the upper surface.

Other fossil specimens

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Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil

Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

sedimentary

Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

sedimentary

Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

fossil

Fossiliferous Limestone

Limestone with embedded fossil cross-section

sedimentary

Fossiliferous Limestone

Fossiliferous Calcilutite / Biomicrite

sedimentary