Rock Identifier
Fossilized Brachiopod (Phylum Brachiopoda (likely Order Spiriferida or Orthida)) — fossil
fossil

Fossilized Brachiopod

Phylum Brachiopoda (likely Order Spiriferida or Orthida)

Hardness: 3 (matrix/calcite) to 7 (if silicified); Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Bilateral symmetry across the valve, often displaying ribbed or costate surfaces. Shell is composed of calcite or phosphate mineralized material.

Hardness
3 (matrix/calcite) to 7 (if silicified)
Color
Gray, tan, or white
Luster
Dull to earthy
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Physical properties

Hardness: 3 (matrix/calcite) to 7 (if silicified); Color: Gray, tan, or white; Luster: Dull to earthy; Structure: Bilateral symmetry across the valve, often displaying ribbed or costate surfaces. Shell is composed of calcite or phosphate mineralized material.

Formation & geological history

Formed in ancient marine environments during the Paleozoic era (approx. 250-540 million years ago) when shells were buried in sediment and lithified into sedimentary rock, often limestone or shale.

Uses & applications

Educational study, paleontological research, and as decorative items for fossil collectors. In the past, fossiliferous limestone has been used as building stone.

Geological facts

Brachiopods are often called 'lamp shells' because they resemble ancient oil lamps. Although they look like clams, they belong to a completely different phylum and are filter feeders with a unique organ called a lophophore.

Field identification & locations

Identify by looking for 'butterfly' or 'fan' shapes in sedimentary rock. They are commonly found in road cuts through limestone, creek beds, and quarries. Look for two valves of different sizes but each with internal symmetry.

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