sedimentary
Chert
Microcrystalline Quartz (SiO2)
Mohs Hardness: 7; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7
- Color
- Grey, brown, or tan
- Luster
- Waxy to dull
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Physical properties
Mohs Hardness: 7; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed from the recrystallization of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation in marine or groundwater environments.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) and strike-a-lights; currently used as road aggregate and in some instances as a gemstone or specimen.
Geological facts
Known as flint when found in chalk or marly limestone; it was one of the first materials used by prehistoric humans to create fire and sharp tools.
Field identification & locations
Identify in the field by its waxy appearance, extreme hardness (scratches glass), and shell-like (conchoidal) fracture edges. Commonly found in limestone beds.
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