sedimentary
Brown Chert
Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Chocolate brown with waxy luster; Crystal structure: Microcrystalline/Cryptocrystalline; Breakage: Conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Chocolate brown with waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Chocolate brown with waxy luster; Crystal structure: Microcrystalline/Cryptocrystalline; Breakage: Conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich micro-organic remains (like radiolaria or diatoms) in marine environments, eventually replacement of carbonate material through chemical precipitation.
Uses & applications
Historically used for stone tools (flintknapping); currently used in road construction as aggregate and as decorative landscaping stone.
Geological facts
Chert and flint are essentially the same material; the name 'flint' is usually reserved for specimens found in chalk. It is so hard it can create sparks when struck against steel.
Field identification & locations
Identify by its smooth, waxy feel when wet and its sharp, glass-like edges when broken. Found globally in limestone formations and as river pebbles.
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