Sedimentary
Gastropod Steinkern (Fossilized Snail Cast)
Phylum Mollusca, Class Gastropoda (Commonly CaCO3 or SiO2 after replacement)
Hardness: 3-4 (if calcite) to 7 (if silicified); Color: Beige, tan, or grey; Luster: Dull/Earthy; Structure: Internal mold (steinkern) showing a spiral or helical coil; Cleavage: None (fractures as rock).
- Hardness
- 3-4 (if calcite) to 7 (if silicified)
- Color
- Beige, tan, or grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 3-4 (if calcite) to 7 (if silicified); Color: Beige, tan, or grey; Luster: Dull/Earthy; Structure: Internal mold (steinkern) showing a spiral or helical coil; Cleavage: None (fractures as rock).
Formation & geological history
Formed when a gastropod shell is filled with sediment (mud or sand), which hardens into rock before the original shell dissolves away. Common in marine deposits from the Paleozoic to Cenozoic eras.
Uses & applications
Used primarily as educational specimens, items for fossil collectors, and sometimes as decorative garden stones if found in large quantities.
Geological facts
The term 'Steinkern' is German for 'stone kernel.' Because snails usually have empty shells after death, they are some of the most common internal mold fossils found in the world.
Field identification & locations
Identify in the field by the distinctive coiled 'cinnamon roll' shape and lack of actual shell surface detail. Commonly found in limestone quarries, road cuts, and dry creek beds.
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