sedimentary
Brown Chert
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Brown to tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Brown to tan
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Brown to tan; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in sedimentary environments via the accumulation of siliceous remains of organisms or chemical precipitation from groundwater. Most specimens range from hundreds of millions to billions of years old.
Uses & applications
Historically used for stone tools and fire-starting. Currently used as road ballast, decorative landscaping stone, and in some gemstone polishing.
Geological facts
Chert is so hard it can scratch steel and was used by ancient civilizations for arrowheads and scrapers due to its sharp, glass-like fracture edge.
Field identification & locations
Identified by its extreme hardness, waxy texture, and smooth curved fractures. Common in riverbeds and limestone outcrops worldwide.
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