sedimentary
Chert (Jasper variation)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown with tan/white bands; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 6
- Color
- Reddish-brown with tan/white bands
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown with tan/white bands; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Can form as nodules or bedded deposits throughout various geological ages.
Uses & applications
Commonly used for lapidary work (jewelry, cabochons), primitive tool making (arrowheads), and as a collector's specimen.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates razor-sharp edges used for blades and scrapers.
Field identification & locations
Identify in the field by its waxy luster and smooth, curved (conchoidal) breaks. It is commonly found in limestone or dolomite beds globally.
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