sedimentary
Fossil Shell Fragment (possibly Brachiopod or Bivalve)
Calcium Carbonate (CaCO3) - Phylum Brachiopoda or Mollusca
Hardness: 3 (Mohs scale); Color: Cream to off-white; Luster: Dull/pearly; Structure: Distinct parallel ribbing/costae; Cleavage: None (concretionary/organic growth); Specific Gravity: ~2.7
- Hardness
- 3 (Mohs scale)
- Color
- Cream to off-white
- Luster
- Dull/pearly
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Physical properties
Hardness: 3 (Mohs scale); Color: Cream to off-white; Luster: Dull/pearly; Structure: Distinct parallel ribbing/costae; Cleavage: None (concretionary/organic growth); Specific Gravity: ~2.7
Formation & geological history
Formed through the accumulation of organic marine remains in shallow sea environments; typically embedded in limestone or shale during the Paleozoic or Mesozoic eras (approx. 66 to 500 million years ago).
Uses & applications
Primarily used for scientific research, education, and as a low-cost entry point for fossil collecting.
Geological facts
Many of these fossils are 'index fossils,' used by geologists to determine the relative age of the rock layers in which they are found. Brachiopods were far more common than clams before the Permian mass extinction.
Field identification & locations
Identify in the field by looking for symmetrical 'fan-like' shapes with ridges in sedimentary limestone outcrops. Common in the American Midwest and fossiliferous regions of Europe.
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