sedimentary
Fossilized Sea Urchin (Echinoid)
Echinoidea (Class) - likely replaced by Calcite or Quartz
Hardness: 3-7 (depending on replacement mineral), Color: Earthy brown to gray, Luster: Dull to vitreous, Structure: Pentamerous symmetry (five-part radial symmetry), typically showing tuberculated plates where spines were attached.
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Physical properties
Hardness: 3-7 (depending on replacement mineral), Color: Earthy brown to gray, Luster: Dull to vitreous, Structure: Pentamerous symmetry (five-part radial symmetry), typically showing tuberculated plates where spines were attached.
Formation & geological history
Forms through permineralization or replacement where a sea urchin is buried in marine sediment. Common in limestone or chalk beds, dating from the Ordovician period to the present.
Uses & applications
Scientific study of evolutionary history, educational specimens, and popular as items for fossil collectors and jewelry.
Geological facts
These are often called 'fairy loaves' or 'shepherd's crowns' in folklore. The bumps on the shell are called tubercles, which served as 'ball-and-socket' joints for the urchin's moving spines.
Field identification & locations
Identify in the field by looking for radial symmetry and a circular or heart-shaped profile in marine sedimentary rock. Found worldwide in ancient seabed deposits.
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