sedimentary
Chert
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Gray, tan, brown with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, brown with waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, tan, brown with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in marine environments through the precipitation of silica or from the accumulation of siliceous remains such as diatoms or radiolarians, often found as nodules in limestone.
Uses & applications
Historically used for stone tools (arrowheads); currently used in road construction, as an abrasive, and occasionally as a decorative landscape stone.
Geological facts
Chert has been used by humans for millions of years because of its ability to fracture into extremely sharp edges. Flint is a high-quality variety of chert.
Field identification & locations
Identify by its waxy appearance, extreme hardness (it will scratch glass), and its characteristic smooth, curved conchoidal fractures.
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