fossil

Fossilized Brachiopod

Brachiopoda (likely Order Spiriferida or Productida)

Commonly looks like a clam shell but with bilateral symmetry across the valves rather than between them. Hardness: 3 (calcite) to 7 (if silicified). Color: Tan, grey, or white. Luster: Dull to pearly. Structure: Two unequal valves.

Hardness: 3 (calcite) to 7 (if silicified)
Color: Tan, grey, or white
Luster: Dull to pearly

Identified July 6, 2026More fossil →

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Physical properties

Formation & geological history

Formed in ancient marine environments when the calcium carbonate shells of marine invertebrates were buried in sediment and lithified. Most common from the Paleozoic era (541 to 252 million years ago).

Uses & applications

Used primarily for scientific research, educational purposes, and as collector items. Occasionally used in jewelry if the fossil has been replaced by agate or opal.

Geological facts

Brachiopods are often called 'lamp shells' because their shape resembles ancient oil lamps. While they look like clams, they are biologically very different and possess a unique feeding organ called a lophophore.

Field identification & locations

Look for symmetrical shell patterns in limestone or shale outcrops. Common in the Midwest USA and UK. Unlike bivalves, one shell (valve) is usually larger than the other and has a small hole for a fleshy foot (pedicle).

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Biogenic Limestone with Brachiopod/Crinoid fragments

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Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

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Fossiliferous Limestone

Limestone with embedded fossil cross-section

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Fossiliferous Limestone with Crinoid stems

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