sedimentary
Chert
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Brownish-tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Brownish-tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in marine environments from the accumulation of silica-rich organic remains like radiolarians or diatoms, or through chemical precipitation in limestone/chalk beds. Commonly Phanerozoic in age.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; currently used as road aggregate, in landscaping, and as a low-cost lapidary material.
Geological facts
Because it breaks with a conchoidal fracture, it was one of the most important materials for prehistoric tool making. It is extremely chemically stable and resistant to weathering.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass), waxy luster, and curved shell-like edges where broken. Commonly found as nodules in limestone regions.
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