sedimentary
Brachiopod Fossil in Shale
Phylum Brachiopoda (often species of Order Spiriferida or Rhynchonellida)
Hardness: 3-4 (matrix), color: grey to dark carbonaceous grey, luster: dull/earthy, structure: bilateral symmetry across the valve (shell), often showing distinct ribbing or costae.
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Physical properties
Hardness: 3-4 (matrix), color: grey to dark carbonaceous grey, luster: dull/earthy, structure: bilateral symmetry across the valve (shell), often showing distinct ribbing or costae.
Formation & geological history
Formed through the lithification of marine mud and silt containing the remains of marine invertebrates. Most common in Paleozoic strata (approx. 541 to 252 million years ago) in shallow sea environments.
Uses & applications
Primarily used for geological dating (index fossils), educational purposes, and private fossil collections. Shale is also a source for ceramic materials and oil/gas exploration.
Geological facts
Brachiopods are 'living fossils'; while they dominate the Paleozoic fossil record, a few species still exist today. Unlike clams, their shells are asymmetrical when viewed from the side but symmetrical across the face.
Field identification & locations
Identify in the field by looking for the fan-shaped 'pedicle' and 'brachial' valves in crumbly, layered sedimentary rock. Commonly found in road cuts and riverbeds in the Midwestern US and the UK.
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