sedimentary
Chert (Flint Nodular)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, yellow-brown, and grey, Luster: waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture). Highly durable and resistant to weathering.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan, yellow-brown, and grey, Luster: waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture). Highly durable and resistant to weathering.
Formation & geological history
Formed through the precipitation of silica from groundwater within limestone or chalk beds. Often associated with Cretaceous or older marine deposits where silica replaced carbonate material.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges. Modernly used as road aggregate, in landscaping, and sometimes for fire-starting (flint).
Geological facts
This specimen appears to be a weathered chert nodule, likely from a glacial or river deposit. Chert can contain microscopic fossils of marine organisms like radiolaria or diatoms.
Field identification & locations
Identify in the field by its waxy texture and shell-like (conchoidal) fracture pattern when broken. It is harder than steel and will scratch glass. Very common in riverbeds and areas with exposed limestone.
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