sedimentary
Chert Pebble
Chert (SiO2)
Hardness: 7 (Mohs scale), Color: Dark grey/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz, Fracture: Conchoidal
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Physical properties
Hardness: 7 (Mohs scale), Color: Dark grey/brown, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz, Fracture: Conchoidal
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in marine environments; age varies by regional geology.
Uses & applications
Commonly used as aggregate in road construction, and historically by indigenous peoples for stone tools due to sharp edges when fractured.
Geological facts
Chert is so hard it can strike sparks against steel. It is chemically very stable and resistant to weathering, which is why it persists as smooth pebbles.
Field identification & locations
Identified by its extreme hardness (scratches glass), smooth texture, and non-granular appearance. Found globally in riverbeds and coastal regions.
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