sedimentary

Gastropod Steinkern (Internal Mold Fossil)

Gastropoda (Class); Internal mold or 'Steinkern' composed of Calcium Carbonate (CaCO3) or Sedimentary matrix

AI-generated identification · may be incorrect

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

Identified March 22, 2026More sedimentary →

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Physical properties

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.