sedimentary

Belemnite Fossil

Belemnitida (Order of extinct cephalopods)

AI-generated identification · may be incorrect

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

Identified March 20, 2026More sedimentary →

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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.