fossil

Fossil Belemnite Guard

Belemnitida (Order), often Hibolites or Neohibolites spp.

AI-generated identification · may be incorrect

Hardness: 3 (calcite); Color: Grey, brown, tan, or white; Luster: Vitreous to dull; Structure: Tapered cylindrical or bullet-shaped rostrum with radial crystalline structure internally.

Hardness: 3 (calcite)
Color: Grey, brown, tan, or white
Luster: Vitreous to dull

Identified July 7, 2026More fossil →

Explore Fossil Belemnite Guard in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 3 (calcite); Color: Grey, brown, tan, or white; Luster: Vitreous to dull; Structure: Tapered cylindrical or bullet-shaped rostrum with radial crystalline structure internally.

Formation & geological history

Formed during the Jurassic and Cretaceous periods (approx. 200-66 million years ago). They are the fossilized internal skeletons (guards/rostra) of extinct cephalopods related to modern squid and cuttlefish, preserved in marine sedimentary rocks.

Uses & applications

Used as educational specimens, collectibles, and occasionally in jewelry or as 'thunderbolts' in folklore. They are also used as index fossils to date geological layers.

Geological facts

In folklore, they were called 'thunderbolts' or 'devil's fingers,' believed to fall from the sky during storms. They are essentially the counter-weight for the prehistoric squid-like creature to maintain balance while swimming.

Field identification & locations

Identify by their distinct bullet-like shape and circular cross-section with radial patterns. Often found on coastlines with eroding Jurassic/Cretaceous cliffs, such as the Jurassic Coast in the UK or parts of the US East Coast.