sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Black, grey, or tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- Black, grey, or tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Black, grey, or tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed from the accumulation of siliceous remains of marine organisms (like diatoms or radiolarians) or inorganic precipitation from silica-rich fluids. Commonly found in limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Today used for road surfacing, as grinding media, and as a sparking agent (flint and steel).
Geological facts
Flint was one of the most important minerals for early humans, enabling the production of sharp cutting edges and the ability to start fires.
Field identification & locations
Identify by its waxy texture and sharp, curved (conchoidal) edges when broken. It is harder than steel and will scratch glass easily.
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