sedimentary
Chert
Chert (SiO2)
Hardness: 7 Mohs; Color: Grey, white, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Grey, white, or tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Grey, white, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains, such as diatoms or radiolarians, or through chemical precipitation in marine environments during various geological periods.
Uses & applications
Historically used for making stone tools (flint knapping) due to its sharp edges. Currently used as road aggregate, in glass manufacturing, and as decorative stone.
Geological facts
Flint is a variety of chert. It was one of the most important materials for early humans to create arrowheads, scrapers, and fire-starting tools.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), its smooth waxy surface, and distinctive curved (conchoidal) fractures when broken.
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