sedimentary
Silicified Gastropod Fossil (Agatized Fossil)
Gastropoda (Class) preserved in Chalcedony/Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Tan, beige, and opaque white; Luster: Waxy to vitreous; Structure: Helical/spiral coil; Cleavage: None (conchoidal fracture)
- Hardness
- 6
- Color
- Tan, beige, and opaque white
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Tan, beige, and opaque white; Luster: Waxy to vitreous; Structure: Helical/spiral coil; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed via permineralization where silica-rich groundwater replaced the organic shell structure of a prehistoric snail within sedimentary layers like limestone or shale.
Uses & applications
Educational specimens, hobbyist collecting, jewelry (when polished), and lapidary art.
Geological facts
Gastropod fossils date back to the Cambrian period. This specific specimen shows 'silicification,' which turns once-brittle shell into durable quartz-based stone.
Field identification & locations
Identify by the distinct spiral 'screw' shape and ridges. Commonly found in eroded creek beds or limestone quarries. Test hardness against steel; it will scratch glass.
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