sedimentary
Gastropod Fossil (Snail Internal Mold)
Gastropoda; internal mold (steinkern), often composed of Calcium Carbonate (CaCO3) or Silica (SiO2)
Hardness: 3-4 (if calcified) or 7 (if silicified); Color: tan, grey, or light brown; Luster: dull to earthy; Structure: planispiral or helicoid coiled shell shape; Cleavage: none (fractures irregularly)
- Hardness
- 3-4 (if calcified) or 7 (if silicified)
- Color
- tan, grey, or light brown
- Luster
- dull to earthy
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Physical properties
Hardness: 3-4 (if calcified) or 7 (if silicified); Color: tan, grey, or light brown; Luster: dull to earthy; Structure: planispiral or helicoid coiled shell shape; Cleavage: none (fractures irregularly)
Formation & geological history
Formed when a snail shell fills with fine sediment or minerals after death. The original shell eventually dissolves, leaving a solid stone cast of the interior. These can range from the Paleozoic to the Cenozoic era, commonly found in limestone or shale beds.
Uses & applications
Primarily used for geological study, education, fossil collecting, and occasionally as decorative pieces in jewelry or 'curiosity' displays.
Geological facts
These specific types of fossils are called 'steinkerns,' a German word meaning 'stone hearts.' They do not show the surface texture of the original shell, but rather an exact replica of the space the animal lived in.
Field identification & locations
Identify by looking for the distinct 'cinnamon roll' or spiral pattern that tapers to a point (apex). Commonly found in sedimentary outcrops, riverbeds, and limestone quarries. Collectors should look for intact coils without heavy erosion.
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