sedimentary
Chert / Quartz Pebble
Microcrystalline Quartz (SiO2)
Hardness 7 on the Mohs scale. Dull to waxy luster, brown to tan color, smooth rounded pebble habit from erosion. Microcrystalline structure with no prominent cleavage.
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Physical properties
Hardness 7 on the Mohs scale. Dull to waxy luster, brown to tan color, smooth rounded pebble habit from erosion. Microcrystalline structure with no prominent cleavage.
Formation & geological history
Formed by the precipitation of silica from groundwater or oceanic sediment, followed by transportation and erosion in stream beds or beaches, rounding the pebble over time.
Uses & applications
Commonly used as decorative gravel, construction aggregate, and historically for stone tool making due to its conchoidal fracture.
Geological facts
Chert pebbles are highly resistant to weathering due to their quartz composition, allowing them to survive long-distance river transport.
Field identification & locations
Identified by its hardness (scratches glass), waxy luster, smooth rounded shape, and smooth conchoidal fracture where chipped. Found globally in riverbeds, beaches, and sedimentary deposits.
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