sedimentary
Belemnite Fossil
Belemnitida (Order of extinct cephalopods)
Hardness: 3-4 (Calcite composition); Color: Gray, brown, or amber-like; Luster: Dull to vitreous; Structure: Cylindrical or bullet-shaped 'rostrum'; Cleavage: None; SG: ~2.7
- Hardness
- 3-4 (Calcite composition)
- Color
- Gray, brown, or amber-like
- Luster
- Dull to vitreous
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Physical properties
Hardness: 3-4 (Calcite composition); Color: Gray, brown, or amber-like; Luster: Dull to vitreous; Structure: Cylindrical or bullet-shaped 'rostrum'; Cleavage: None; SG: ~2.7
Formation & geological history
Formed from the internal calcified shell (rostrum) of squid-like cephalopods that lived during the Jurassic and Cretaceous periods (approx. 200–66 million years ago) in marine environments.
Uses & applications
Used primarily for fossil collecting, educational purposes, and occasionally in jewelry as polished stones or pendants.
Geological facts
Commonly known as 'thunderbolts' in folklore, as they were once believed to be cast down from the sky during storms. They are an important index fossil for dating marine sediment layers.
Field identification & locations
Identify by its distinctive bullet shape and circular cross-section showing radial growth lines. Found commonly in chalk or limestone cliffs, such as the Jurassic Coast in the UK or various US marine deposits.
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