sedimentary
Chert (Jasper/Flint variety)
Microcrystalline quartz (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Brownish-grey with waxy luster, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Brownish-grey with waxy luster, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in groundwater; typically found in nodules or bedded deposits throughout geological ages.
Uses & applications
Used historically for stone tools and weapons; currently used for decorative purposes, lapidary work, and landscaping.
Geological facts
Chert was one of the first materials used by early humans for tools because its conchoidal fracture creates extremely sharp edges.
Field identification & locations
Identify by its waxy luster, hardness (will scratch glass), and the way it breaks into smooth curved surfaces. Found worldwide in limestone and chalk deposits.
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