sedimentary
Chert (Flint)
Chert (Cryptocrystalline silicon dioxide, SiO2)
Hardness: 7 Mohs; Color: Grey, tan, brown with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Grey, tan, brown with waxy luster
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Physical properties
Hardness: 7 Mohs; Color: Grey, tan, brown with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Forms from the accumulation of siliceous remains of marine organisms or through chemical precipitation in sedimentary environments. Can be found in limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires; currently used in construction aggregate, road surfacing, and as a decorative stone.
Geological facts
Flint was the primary material for prehistoric toolmaking because it fractures into extremely sharp edges. It is a variety of chert commonly associated with chalk or marly limestone.
Field identification & locations
Identify by its waxy luster, smooth conchoidal (shell-like) fracture, and the fact that it can scratch glass. Common in river beds and sedimentary outcrops.
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