sedimentary
Gastropod Steinkern (Internal Mold Fossil)
Gastropoda (Class); Internal mold or 'Steinkern' composed of Calcium Carbonate (CaCO3) or Sedimentary matrix
Hardness: 3 (if calcite) to 6 (if silicified); Color: Tan, beige, or off-white with orange-ish iron staining; Luster: Dull to earthy; Structure: Spiral or helical screw-like form; Cleavage: None (conchoidal fracture if broken)
- Hardness
- 3 (if calcite) to 6 (if silicified)
- Color
- Tan, beige, or off-white with orange-ish iron staining
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (if calcite) to 6 (if silicified); Color: Tan, beige, or off-white with orange-ish iron staining; Luster: Dull to earthy; Structure: Spiral or helical screw-like form; Cleavage: None (conchoidal fracture if broken)
Formation & geological history
Formed when a snail shell was filled with fine sediment or minerals that hardened over millions of years. The original shell eventually dissolved, leaving the 'cast' of the interior. Most common in marine sedimentary layers ranging from the Paleozoic to the Cenozoic era.
Uses & applications
Educational specimens for classrooms, personal fossil collections, and biological studies used to date sedimentary rock layers (biostratigraphy).
Geological facts
The word 'Steinkern' is German for 'stone kernel.' These fossils represent the negative space inside an organism rather than the organism's shell itself. They are common in limestone and chalk deposits.
Field identification & locations
Identify by looking for distinct spiral whorls (spires) that lack external shell texture or ornamentation. Common in ancient reef or seabed deposits. Collection involves checking limestone outcrops or creek beds in sedimentary regions.
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