Fossilized Brachiopod

Physical Properties

Hardness: 3 (if calcite replacement); Color: Grey, beige, tan; Luster: Dull to earthy; Structure: Bilateral symmetry with curved growth lines; Cleavage: None (fossilized structure).

Formation & Geological History

Formed in marine environments through the replacement of shell material with minerals after the organism was buried in sediment. These typically date from the Paleozoic era (541 to 252 million years ago).

Uses & Applications

Educational purposes, geological research, and popular for amateur fossil collecting.

Geological Facts

Brachiopods look like clams but are biologically distinct; they filter food using a unique organ called a lophophore. They were once the most abundant shellfish in Earth's oceans.

Field Identification & Locations

Identify in the field by looking for 'lamp shell' shapes with distinct growth ridges appearing in limestone or shale outcrops. Extremely common in the Midwest US and UK.

Identified on: 5/3/2026

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