sedimentary
Chert / Flint
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 7 on Mohs scale; Color: Light beige, tan, cream, to light brown; Luster: Waxy to dull; Fracture: Conchoidal; Density: ~2.65 g/cm3
- Hardness
- 7 on Mohs scale
- Color
- Light beige, tan, cream, to light brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Light beige, tan, cream, to light brown; Luster: Waxy to dull; Fracture: Conchoidal; Density: ~2.65 g/cm3
Formation & geological history
Formed through the accumulation of siliceous oozes or precipitation of silica-rich fluids within marine sedimentary rocks like limestone and chalk.
Uses & applications
Historically used for stone tools and knapping arrowheads; modernly used as road aggregate, ballast, and occasionally decorative landscaping stone.
Geological facts
Chert produces sparks when struck against iron or steel, making it essential for ancient fire-starting techniques and flintlock firearms.
Field identification & locations
Look for a microcrystalline, smooth texture with shell-like (conchoidal) fracture lines and sharp edges. Extremely common in limestone formations, stream beds, and gravel pits.
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