sedimentary
Fossilized Sea Urchin Spines
Echinoidea (Cidaroid spines)
Hardness: 3 (calcite); Color: Pale grey, tan, or greenish; Luster: Dull to earthy; Shape: Cylindrical, tapered, or club-shaped with a basal attachment ring; Cleavage: Rhombohedral (if recrystallized).
- Hardness
- 3 (calcite)
- Color
- Pale grey, tan, or greenish
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (calcite); Color: Pale grey, tan, or greenish; Luster: Dull to earthy; Shape: Cylindrical, tapered, or club-shaped with a basal attachment ring; Cleavage: Rhombohedral (if recrystallized).
Formation & geological history
Formed through the permineralization of sea urchin spines in marine environments. These specimens are typically from the Cretaceous or Jurassic periods (approx. 66–200 million years ago) and are often found in limestone or chalk deposits.
Uses & applications
Used primarily as educational specimens, collector's items, and occasionally in eccentric jewelry pieces.
Geological facts
In folklore, particularly in England, these fossils were sometimes called 'thunderbolts' or 'fairy bolts.' Unlike modern urchins whose spines fall off easily after death, these thicker club-like cidaroid spines are more robust and more likely to fossilize.
Field identification & locations
Identify in the field by their distinct symmetrical ridging or 'warts' on the surface and the circular attachment point at the base. Commonly found in limestone quarries or coastal chalk cliffs.
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