sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Brownish-tan with waxy/earthy luster; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like)
- Hardness
- 6
- Color
- Brownish-tan with waxy/earthy luster
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Brownish-tan with waxy/earthy luster; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like)
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms or via chemical precipitation from silica-rich fluids in sedimentary basins. Often found in nodules or bedded layers.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; currently used for lapidary work, decorative landscaping, and as an abrasive in some industrial contexts.
Geological facts
Chert has been used by humans for over 2 million years to create tools. It sparks when struck against steel, making it vital for early fire-starting and flintlock firearms.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel nail), smooth waxy texture, and sharp, curved fracture edges. Common in limestone riverbeds and desert pavement.
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