sedimentary
Flint (Chert)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Black, dark grey, or brown; Luster: Waxy or dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Black, dark grey, or brown
- Luster
- Waxy or dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Black, dark grey, or brown; Luster: Waxy or dull; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed as nodules in sedimentary rocks like chalk or limestone via the concentration of silica from organic sources (sponges, diatoms) during diagenesis.
Uses & applications
Historically used for stone tools and weapons (arrowheads); currently used in road construction, flintlock mechanisms, and as decorative stone.
Geological facts
Flint was the primary technology for early humans; when struck against steel or pyrite, it produces sparks due to the friction oxidizing the metal particles.
Field identification & locations
Identify by its characteristic curved, shell-like (conchoidal) fractures and sharp edges. It is extremely common in the chalk downs of England and Northern Europe.
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