sedimentary
Chert (Flint pebble)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale. Color: Gray, tan, white, and dark brown/black banding. Luster: Dull to waxy. Crystal Structure: Microcrystalline (trigonal). Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, white, and dark brown/black banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale. Color: Gray, tan, white, and dark brown/black banding. Luster: Dull to waxy. Crystal Structure: Microcrystalline (trigonal). Cleavage: None (conchoidal fracture).
Formation & geological history
Chert forms through chemical weathering and precipitation of silica-rich fluids in sedimentary basins or marine environments, often replacing organic carbonate material or precipitating out of solution.
Uses & applications
Historically used for stone tools, arrowheads, and fire-starting flint. Today, used as road aggregate, construction material, and decorative landscaping pebble.
Geological facts
Chert and flint produce sharp conchoidal fractures when struck, making them essential materials for early human technology during the Stone Age.
Field identification & locations
Identified by its extreme hardness (scratches glass), waxy to dull texture, and sharp, shell-like (conchoidal) fracture edges. Commonly found along riverbeds, beaches, and chalk/limestone formations worldwide.
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