sedimentary

Echinoid Fossil (Sea Urchin)

Echinoidea (specifically likely Schizaster or similar genus), calcium carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 (calcite preservation). Color: Tan, brown, or gray. Luster: Dull/earthy. Crystal structure: Trigonal (as calcite replacement). Features: Distinct five-fold radial symmetry (pentamerism) often visible as star-shaped patterns on the top.

Hardness: 3 (calcite preservation)
Color: Tan, brown, or gray
Luster: Dull/earthy

Identified March 31, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environments through the mineralization of sea urchin exoskeletons. These typically range from the Ordovician period to the present, with many common specimens dating to the Cretaceous or Paleogene (approx. 66–23 million years ago).

Uses & applications

Primarily used for educational purposes, scientific study, and as decorative items for fossil collectors. In some cultures, they have been used as amulets or 'thunderstones'.

Geological facts

Commonly known as 'shepherd's crowns' or 'fairy loaves' in English folklore, they were historically believed to protect against witchcraft or ensure bread always rose in the oven.

Field identification & locations

Identify in the field by looking for disc-like or heart-shaped stones with a clear star pattern on one side and a rough, pitted texture. Commonly found in limestone quarries, chalk deposits, or coastal cliffs (e.g., Texas, UK, France).