sedimentary
Chert (Yellow Jasper variant)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Yellowish-brown to tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline, Fracture: Conchoidal
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Yellowish-brown to tan, Luster: Waxy to dull, Crystal Structure: Microcrystalline/Cryptocrystalline, Fracture: Conchoidal
Formation & geological history
Formed through the accumulation of silica-rich fluids in sedimentary environments or by the precipitation of chemical silica from groundwater replacing organic material or carbonate rocks.
Uses & applications
Used historically for stone tools due to its sharp edges; modern uses include lapidary work, jewelry, and as a decorative stone in aquariums and landscaping.
Geological facts
Chert is so durable that it often survives long after the surrounding rock has weathered away. The yellow color is usually caused by trace amounts of iron oxide (goethite).
Field identification & locations
Identify by its characteristic conchoidal fracture (curved, shell-like breaks) and that it cannot be scratched by a steel knife. Commonly found in stream beds and coastal areas.
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