sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Tan, brown, grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 6
- Color
- Tan, brown, grey
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Tan, brown, grey; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed as nodules or layers in limestone through the accumulation of silica-rich organic remains or chemical precipitation. Found in Paleozoic to Cenozoic strata.
Uses & applications
Historically used for stone tools and starting fires; modernly used as road aggregate and in some jewelry as 'Jasper' or decorative stones.
Geological facts
Chert was one of the most vital materials for early humans because of its conchoidal fracture, which creates razor-sharp edges for knives and arrowheads.
Field identification & locations
Identify by its ability to scratch glass and its shell-like (conchoidal) breakage patterns. Commonly found in limestone outcrops or riverbeds.
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