sedimentary
Fossilized Gastropod (Snail)
Class Gastropoda (internal mold or 'steinkern')
Hardness: 3-4 (if calcified) or 6-7 (if silicified); Color: Gray, tan, or brown; Luster: Dull to earthy; Structure: Spiral or helical coil; Cleavage: None (fractures like the matrix rock); Specific Gravity: ~2.6-2.7.
- Hardness
- 3-4 (if calcified) or 6-7 (if silicified)
- Color
- Gray, tan, or brown
- Luster
- Dull to earthy
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Physical properties
Hardness: 3-4 (if calcified) or 6-7 (if silicified); Color: Gray, tan, or brown; Luster: Dull to earthy; Structure: Spiral or helical coil; Cleavage: None (fractures like the matrix rock); Specific Gravity: ~2.6-2.7.
Formation & geological history
Formed when a snail shell was buried in sediment; the hollow interior filled with minerals (mud/sand/calcite) which hardened. Over time, the original organic shell dissolved, leaving behind a stone 'internal mold' or cast. Common in limestone and shale formations across various geological eras from the Paleozoic to the Cenozoic.
Uses & applications
Educational specimens for geology students; used in fossil kits; decorative objects for private collections; paleoclimatic indicators for environmental research.
Geological facts
Gastropods are one of the few classes of animals to have successfully inhabited the ocean, freshwater, and land. When you find one that looks like a smooth stone spiral without a shell, it is called a 'steinkern', which is German for 'stone heart'.
Field identification & locations
Identify in the field by looking for distinct spiral/screw-like geometry in sedimentary rock layers. Often found in dry creek beds, limestone quarries, or coastal cliffs. Collectors should check for the presence of 'whorls' or steps in the spiral.
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