sedimentary
Bivalve Fossil (Internal Mold/Steinkern)
Class Bivalvia (Fossilized Mold)
Hardness: 3-4 (calcite Replacement). Color: Cream to tan. Luster: Dull/Earthy. Cleavage: None. Structure: Symmetrical fan-shape with prominent ribs.
- Hardness
- 3-4 (calcite Replacement)
- Color
- Cream to tan
- Luster
- Dull/Earthy
Identified More sedimentary →
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Physical properties
Hardness: 3-4 (calcite Replacement). Color: Cream to tan. Luster: Dull/Earthy. Cleavage: None. Structure: Symmetrical fan-shape with prominent ribs.
Formation & geological history
Formed in marine sedimentary environments where a shellfish was buried by sediment. Over time, the organic shell dissolved, leaving a mineral-filled cast or mold within limestone or sandstone layers.
Uses & applications
Used primarily as educational specimens, for paleontological research, and as decorative items for fossil collectors.
Geological facts
Bivalves have existed since the Cambrian period (~500 million years ago) and survived multiple mass extinctions. This specimen specifically shows the 'steinkern' or internal mud-filling of the shell.
Field identification & locations
Identified by its distinctive ribbed, hinged shell appearance. Common in limestone outcrops, road cuts, and ancient sea beds.
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