sedimentary
Brachiopod Fossil
Phylum Brachiopoda (Class Rhynchonellata)
Hardness: 3 (if calcite replacement) to 7 (if silicified); Color: tan, grey, or brown; Luster: dull to earthy; Structure: bilateral symmetry across the valve; Cleavage: none; Specific Gravity: approx 2.7.
- Hardness
- 3 (if calcite replacement) to 7 (if silicified)
- Color
- tan, grey, or brown
- Luster
- dull to earthy
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Physical properties
Hardness: 3 (if calcite replacement) to 7 (if silicified); Color: tan, grey, or brown; Luster: dull to earthy; Structure: bilateral symmetry across the valve; Cleavage: none; Specific Gravity: approx 2.7.
Formation & geological history
Formed through the fossilization of marine invertebrate shells in sedimentary environments, typically during the Paleozoic era (approx. 250-500 million years ago) via permineralization or recrystallization.
Uses & applications
Primarily used for scientific research, geological dating (index fossils), and as popular collector items for hobbyists.
Geological facts
Brachiopods look like clams but are unrelated; they have a pedicle (stalk) to anchor to the seafloor. They were once the most abundant shelled creatures on Earth before the Permian-Triassic extinction.
Field identification & locations
Identify by radial ridges (costae) and a hinge line. Commonly found in limestone or shale outcrops and riverbeds in the Midwestern United States and Europe.
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