sedimentary
Chert / River Pebble
Silicon Dioxide (SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, beige, brown with iron staining, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), SG: 2.6
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan, beige, brown with iron staining, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), SG: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary basins. This specimen appears water-worn from a river or glacial environment.
Uses & applications
Historically used for stone tools (arrowheads) due to its sharp fracture; currently used in construction aggregate, landscaping, or as a pocket stone for collectors.
Geological facts
Chert is extremely durable and chemically stable, allowing it to survive long-distance transport in rivers and glacial till while other softer minerals weather away.
Field identification & locations
Identify by its hardness (will scratch glass), smooth waxy feel, and rounded shape. Found globally in riverbeds, beaches, and gravel pits.
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