fossil
Bivalve Fossil (Clam)
Class Bivalvia (e.g., Exogyra or Gryphaea species)
Hardness: 3 (calcite) to 7 (if silicified); Color: Grey, tan, or white; Luster: Dull/earthy; Shell-like curved structure with growth lines; Composition: Calcium carbonate or Replacement silica.
- Hardness
- 3 (calcite) to 7 (if silicified)
- Color
- Grey, tan, or white
- Luster
- Dull/earthy
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Physical properties
Hardness: 3 (calcite) to 7 (if silicified); Color: Grey, tan, or white; Luster: Dull/earthy; Shell-like curved structure with growth lines; Composition: Calcium carbonate or Replacement silica.
Formation & geological history
Formed through the burial and mineral replacement of marine mollusks in sedimentary environments. Common in limestone or shale beds from the Paleozoic to Cenozoic eras.
Uses & applications
Scientific study, educational displays, and personal fossil collections.
Geological facts
Bivalves have existed for over 500 million years. Some fossilized specimens are used to date the geological layers in which they are found, known as index fossils.
Field identification & locations
Identify by looking for bilateral symmetry between valves and concentric growth lines. Commonly found in road cuts, creek beds, and quarries containing marine sedimentary rock.
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