sedimentary
Yellow Chert (Cherty Pebble)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Yellow-brown/tan, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Yellow-brown/tan, Luster: Waxy to dull, Crystal Structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary environments. This specimen appears water-worn, likely from a riverbed or coastal environment.
Uses & applications
Historically used for stone tools/arrowheads. Modernly used in landscaping, as tumbling rough for hobbyists, or as road aggregate.
Geological facts
Chert is so durable that it often survives long after the surrounding rock has eroded. Yellow chert gets its distinct color from iron oxide (limonite) impurities within the silica structure.
Field identification & locations
Identify by its hardness (will scratch glass), waxy feel, and smooth, rounded edges if found in water. Common in limestone deposits and river gravels worldwide.
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