sedimentary
Belemnoidea (Belemnite Guard)
Belemnitida (calcitic rostrum)
Hardness: 3 (calcite); Color: Grey, brown, or translucent yellow; Luster: Vitreous to dull; Structure: Bullet-shaped or conical internal skeleton with radial crystallization.
- Hardness
- 3 (calcite)
- Color
- Grey, brown, or translucent yellow
- Luster
- Vitreous to dull
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Physical properties
Hardness: 3 (calcite); Color: Grey, brown, or translucent yellow; Luster: Vitreous to dull; Structure: Bullet-shaped or conical internal skeleton with radial crystallization.
Formation & geological history
Fossilized internal remains of extinct cephalopods from the Jurassic and Cretaceous periods (approx. 200–66 million years ago). Formed within marine sediments.
Uses & applications
Scientific study, educational collections, and occasionally used in jewelry or as 'thunderstones' in folklore.
Geological facts
In folklore, they were believed to be 'thunderbolts' cast from the sky during storms. They are the ancient ancestors of modern squids and cuttlefish.
Field identification & locations
Identify by its distinctive bullet shape, circular cross-section, and radiating calcite crystal structure inside when broken. Commonly found in chalk or limestone cliffs.
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