sedimentary
Belemnite (Fossilized Rostrum)
Belemnitida (Order), composed of Calcite (CaCO3)
Hardness: 3 (Mohs scale); Color: amber, brown, or grey; Luster: vitreous to dull; Crystal structure: fibrous crystalline calcite; Cleavage: none; Specific gravity: 2.7
- Hardness
- 3 (Mohs scale)
- Color
- amber, brown, or grey
- Luster
- vitreous to dull
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Physical properties
Hardness: 3 (Mohs scale); Color: amber, brown, or grey; Luster: vitreous to dull; Crystal structure: fibrous crystalline calcite; Cleavage: none; Specific gravity: 2.7
Formation & geological history
Belemnites were cephalopods similar to modern squid. The fossil found is the 'rostrum,' a hard internal tail part that settled in marine sediment during the Jurassic and Cretaceous periods (approx. 200–66 million years ago).
Uses & applications
Primary use is in scientific study (stratigraphy) and as educational/collector specimens. They are occasionally polished for use in jewelry or sold as curiosities.
Geological facts
In folklore, they were known as 'Thunderbolts' because people believed they fell from the sky during storms. They are an extinct group of cephalopods related to cuttlefish.
Field identification & locations
Identify by its bullet-like shape, circular cross-section, and radiating crystalline structure inside. Commonly found in coastal chalk cliffs and marine sedimentary layers globally (e.g., Jurassic Coast, UK).
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