sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, reddish-orange; Luster: Dull to waxy; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: none (fractures conchoidally); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, reddish-orange
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, reddish-orange; Luster: Dull to waxy; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: none (fractures conchoidally); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools/weapons; currently used for road surfacing, jewelry (as semi-precious Jasper), and as a fire-starting material.
Geological facts
Chert was one of the most important materials for early humans because of its ability to be chipped into sharp edges. Reddish varieties colored by iron oxide are commonly called Jasper.
Field identification & locations
Identify in the field by its hardness (it can scratch glass), its smooth 'shell-like' conchoidal fracture, and its waxy appearance when wet or polished. Often found in riverbeds or gravel deposits.
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