sedimentary
Chert
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Pale green, gray, tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Pale green, gray, tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: Pale green, gray, tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools and weapons; currently used in decorative landscaping, construction aggregate, and as a collectible river stone.
Geological facts
Chert has a conchoidal fracture which produces sharp edges, making it the preferred material for prehistoric arrowheads and scrapers.
Field identification & locations
Identify by its hardness (scratches glass), waxy feel, and smooth curved fractures when broken; commonly found in stream beds and coastal areas.
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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