fossil

Belemnite Fossil

Belemnitida (rostrum)

Hardness: 3-4 (calcite); Color: Dark grey, brown, or black; Luster: Vitreous to dull; Crystal structure: Trigonal (calcite replacement); Cleavage: Perfect rhombohedral in calcite; Specific Gravity: 2.7

Hardness: 3-4 (calcite)
Color: Dark grey, brown, or black
Luster: Vitreous to dull

Identified August 5, 2026More fossil →

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Physical properties

Formation & geological history

Formed during the Mesozoic era (Jurassic to Cretaceous periods, approximately 200 to 66 million years ago) from the calcified internal guards (rostra) of ancient squid-like cephalopods.

Uses & applications

Used as index fossils for dating geological strata, valued by fossil collectors and educational displays.

Geological facts

Commonly known as 'thunderbolts' or 'devil's fingers' in folklore due to the ancient belief that they fell from the sky during lightning storms.

Field identification & locations

Found worldwide in marine sedimentary rocks, especially chalk and limestone formations. Easily identified by their elongated, bullet-like or cigar-like cylindrical shape, tapering to a point, often showing a central tubular cavity (the alveolus) at the wider end.