sedimentary
Gastropod Fossil (Internal Mold)
Phylum Mollusca, Class Gastropoda (Steinkern)
Hardness: 3-4 (Calcite/Sedimentary matrix); Color: Tan, beige, or white; Luster: Dull/Earthy; Structure: Spiral or helical coil (high-spired); Cleavage: None (conchoidal fracture when broken)
- Hardness
- 3-4 (Calcite/Sedimentary matrix)
- Color
- Tan, beige, or white
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (Calcite/Sedimentary matrix); Color: Tan, beige, or white; Luster: Dull/Earthy; Structure: Spiral or helical coil (high-spired); Cleavage: None (conchoidal fracture when broken)
Formation & geological history
Formed when the hollow interior of a snail shell was filled with sediment like mud or sand, which then lithified. Over time, the original organic shell often dissolves, leaving behind this three-dimensional internal cast or 'steinkern'. Ages can range from the Paleozoic to Cenozoic eras.
Uses & applications
Scientific study of paleoenvironments, educational tools, and hobbyist collecting.
Geological facts
This specific type of fossil is known as a 'steinkern', German for 'stone kernel'. It does not show the outer surface of the shell, but rather the shape of the animal's interior cavity.
Field identification & locations
Identify in the field by looking for spiral, screw-like shapes in limestone or shale outcrops. Common in ancient marine deposit areas. Collectors should look for distinct whorls and a preserved apex.
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