sedimentary
Chert (Flint variety)
Chert (SiO2)
Hardness: 7 on Mohs scale; Color: Grey, tan, or brown with waxy luster; Crystal Structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Grey, tan, or brown with waxy luster
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Physical properties
Hardness: 7 on Mohs scale; Color: Grey, tan, or brown with waxy luster; Crystal Structure: Microcrystalline/Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or through the chemical precipitation of silica in groundwater. Found in marine or lacustrine sedimentary layers.
Uses & applications
Historically used for stone tools (arrowheads, scrapers); currently used as an abrasive, in road construction, and for decorative landscaping.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges; it was also used in early firearms as 'flint' to create sparks.
Field identification & locations
Identify by its 'flint-like' appearance, waxy texture on broken surfaces, and inability to be scratched by a steel knife. It will also spark when struck against steel. Found globally in limestone formations.
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