sedimentary
Chert (Yellow Jasper/Flint)
Chert (Microcrystalline Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan to yellowish-brown, Luster: waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan to yellowish-brown, Luster: waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65
Formation & geological history
Formed primarily from the accumulation of siliceous remains of marine organisms or via precipitation of silica-rich fluids in limestone or chalk beds. This specific specimen appears to be a water-worn river pebble.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) due to its sharp edges; modern uses include landscaping, road gravel, and as a decorative stone in jewelry (when classified as jasper).
Geological facts
Chert is so hard it can create sparks when struck against steel, which made it vital for flintlock firearms. It was one of the most important minerals for early human technological development.
Field identification & locations
Identified in the field by its hardness (cannot be scratched by a steel knife), its smooth waxy feel, and its characteristic curved (conchoidal) breaks. Extremely common in riverbeds and sedimentary basins worldwide.
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