sedimentary
Chert
Chert (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs scale; Color: typically gray, brown, or tan; Luster: dull to waxy; Structure: microcrystalline or cryptocrystalline; Cleavage: none, conchoidal fracture.
- Hardness
- 7 Mohs scale
- Color
- typically gray, brown, or tan
- Luster
- dull to waxy
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Physical properties
Hardness: 7 Mohs scale; Color: typically gray, brown, or tan; Luster: dull to waxy; Structure: microcrystalline or cryptocrystalline; Cleavage: none, conchoidal fracture.
Formation & geological history
Formed in marine environments through the accumulation of siliceous remains of organisms like diatoms and radiolarians, or via chemical precipitation from silica-rich fluids.
Uses & applications
Historically used for making stone tools (flint knapping); currently used as road base, construction aggregate, and occasionally for lapidary work.
Geological facts
Chert is so hard it can scratch glass. It is often found as nodules within limestone or dolomite beds. Flint is a specific dark variety of chert.
Field identification & locations
Identified by its extreme hardness, smooth conchoidal (shell-like) fracture surfaces, and waxy texture. Extremely common in sedimentary basins worldwide.
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