Fossilized Brachiopod Shell in Matrix

Physical Properties

Hardness: 3 (calcite); Color: Cream, grey, or tan; Luster: Dull to pearly; Structure: Bilaterally symmetrical shell valves; Cleavage: None (conchoidal fracture when broken)

Formation & Geological History

Formed in marine environments as biological debris that becomes buried in sediment; most common in Paleozoic (541–252 million years ago) limestone and shale deposits.

Uses & Applications

Scientific study (paleontology), educational tools, and hobbyist collecting; some large specimens used for decorative display.

Geological Facts

Brachiopods are sometimes called 'lamp shells' because they resemble ancient Roman oil lamps. While they look like clams, they are biologically distinct and have a different internal anatomy.

Field Identification & Locations

Identify by looking for symmetrical 'butterfly' or 'wing' shapes embedded in limestone. Found globally in ancient seabed deposits, particularly in the Midwestern United States.

Identified on: 5/19/2026

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