sedimentary
Chert (Jasper)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Reddish-brown, gray, tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown, gray, tan
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown, gray, tan; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments, often deep sea or limestone replacement. Found across all geological ages.
Uses & applications
Historically used for stone tools (arrowheads). Currently used for lapidary work, jewelry, landscaping, and construction aggregate.
Geological facts
Red specimens are often referred to as Jasper. Because of its conchoidal fracture, it was one of the most important materials for early humans to create sharp-edged tools.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and smooth, curved (conchoidal) breaks. Commonly found in riverbeds or as nodules in limestone.
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