mineral
Quartz Pebble (River Agate / Chalcedony)
Silicon Dioxide (SiO2)
Hardness 7 on Mohs scale, translucent yellowish-brown to tan color, vitreous to waxy luster, trigonal/hexagonal crystal system, conchoidal fracture, specific gravity ~2.65.
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Physical properties
Hardness 7 on Mohs scale, translucent yellowish-brown to tan color, vitreous to waxy luster, trigonal/hexagonal crystal system, conchoidal fracture, specific gravity ~2.65.
Formation & geological history
Formed via precipitation of silica-rich fluids in cavities within sedimentary, metamorphic, or igneous rocks, then weathered and naturally rounded by water transport in riverbeds or ocean beaches.
Uses & applications
Popular for lapidary art, rock tumbling, cabochon cutting, jewelry making, and general rockhounding collecting.
Geological facts
Natural river-tumbled quartz pebbles often feature 'chatter marks' or tiny crescent impact marks caused by rolling along riverbeds and colliding with other rocks over thousands of years.
Field identification & locations
Identified by its harness (scratches glass easily), waxy to greasy luster, lack of cleavage, and translucent brown/amber tone. Commonly found along river gravel bars, lakeshores, and alluvial beaches worldwide.
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