sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids in limestone or chalk beds.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) and starting fires (flint and steel). Modern uses include road surfacing and as a minor component in glass production.
Geological facts
Cultures around the world have prized chert for millennia because its conchoidal fracture creates edges sharper than a steel scalpel.
Field identification & locations
Identify in the field by its waxy texture and sharp, shell-like (conchoidal) edges when broken. It will often spark when struck against steel.
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