sedimentary
Fossilized Brachiopod
Phylum Brachiopoda (General mineral composition: Calcite/CaCO₃ or Silica/SiO₂)
Hardness: 3 (if calcite) to 7 (if silicified); Color: Tan, brown, or grey; Luster: Dull to earthy; Crystal structure: Often replaces biological structure with microcrystalline quartz or calcite; Cleavage: None (conchoidal fracture if silicified).
- Hardness
- 3 (if calcite) to 7 (if silicified)
- Color
- Tan, brown, or grey
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (if calcite) to 7 (if silicified); Color: Tan, brown, or grey; Luster: Dull to earthy; Crystal structure: Often replaces biological structure with microcrystalline quartz or calcite; Cleavage: None (conchoidal fracture if silicified).
Formation & geological history
Formed through permineralization or replacement of marine seashells in sedimentary basins. Most common specimens date from the Paleozoic Era (approx. 541 to 252 million years ago) in shallow sea environments.
Uses & applications
Primarily used for educational purposes, scientific research (stratigraphy), and as collector's items. Larger/well-preserved pieces can be used in jewelry or as decorative paperweights.
Geological facts
Brachiopods look like clams but are biologically distinct; they have a 'pedicle' (fleshy stalk) and symmetrical valves. They were one of the most abundant life forms on Earth before the Permian-Triassic extinction event.
Field identification & locations
Identify in the field by looking for 'lamp shell' shapes with distinct ribbing (costae) or a fold and sulcus. Commonly found in limestone outcrops, road cuts, or dry creek beds in areas with ancient seabed deposits.
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