sedimentary
Banded Chert
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs), Color: Dark grey with brown/tan bands, Luster: Waxy to vitreous when polished, Crystal structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Dark grey with brown/tan bands, Luster: Waxy to vitreous when polished, Crystal structure: Microcrystalline/cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine or lacustrine environments; often found in Precambrian to Cenozoic strata.
Uses & applications
Used historically for stone tools and weapons due to its sharp edges; currently used for lapidary work, tumbling, and as decorative gravel.
Geological facts
Chert was a primary material for prehistoric hunter-gatherers to make arrowheads and scrapers. Flint is a common variety of dark chert.
Field identification & locations
Identify by its waxy luster, hardness (scratches glass), and the way it breaks into smooth, curved surfaces (conchoidal fracture). Commonly found in stream beds and coastal areas.
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