Belemnite Fossil (Guard)

Physical Properties

Hardness: 3-4 (Mohs scale); Color: Brown, gray, or tan; Luster: Dull to waxy; Structure: Cylindrical or bullet-shaped with a characteristic internal radial structure; Cleavage: None (fractures); Specific Gravity: ~2.7

Formation & Geological History

Formed as the internal skeleton (rostrum) of extinct cephalopods. These lived during the Mesozoic era (Jurassic to Cretaceous periods), specifically between 200 and 66 million years ago. They are typically found in seafloor sediment that has compressed into limestone or shale.

Uses & Applications

Primarily used for educational purposes, paleontological study, and as decorative jewelry or collector's items.

Geological Facts

In medieval times, these fossils were called 'thunderbolts' or 'devil's fingers' and were believed to have fallen from the sky during storms or were thought to have medicinal properties to cure kidney stones.

Field Identification & Locations

Identify in the field by their distinct bullet shape and a circular cross-section that often shows radiating rays of calcite. They are commonly found in 'Belemnite graveyards' where thousands of individuals washed up together in specific sedimentary layers.

Identified on: 4/26/2026

Mode: Standard