sedimentary
Fossilized Brachiopod Shell in Matrix
Phylum Brachiopoda (typically Calcium Carbonate or Chitinophosphatic)
Hardness: 3 (calcite); Color: Cream, grey, or tan; Luster: Dull to pearly; Structure: Bilaterally symmetrical shell valves; Cleavage: None (conchoidal fracture when broken)
- Hardness
- 3 (calcite)
- Color
- Cream, grey, or tan
- Luster
- Dull to pearly
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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.
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