sedimentary
Brachiopod Fossil
Phylum Brachiopoda (likely Order Rhynchonellida or Spiriferida)
Hardness: 3-4 (calcite), Color: Tan to grey, Luster: Dull/Earthy, Crystal Structure: Amorphous (biogenic mineral), Specific Gravity: 2.7
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Physical properties
Hardness: 3-4 (calcite), Color: Tan to grey, Luster: Dull/Earthy, Crystal Structure: Amorphous (biogenic mineral), Specific Gravity: 2.7
Formation & geological history
Formed through the fossilization of marine organisms in limestone or shale beds; commonly dating from the Paleozoic era (approx. 250-500 million years ago) during the Ordovician or Devonian periods.
Uses & applications
Primarily for educational purposes, paleontological study, and fossil collecting; index fossils for dating geological strata.
Geological facts
Brachiopods are often called 'lamp shells' because they resemble ancient oil lamps. Although they look like clams (mollusks), they are biologically distinct and have upper/lower valves rather than left/right valves.
Field identification & locations
Identify by looking for bilateral symmetry across the surface of the shell and prominent radial ribbing. Commonly found in roadcuts and creek beds in regions with limestone bedrock like the American Midwest.
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