sedimentary
Quartz Pebble (Iron-stained Chalcedony / Chert)
Silicon Dioxide (SiO2)
Hardness 7 on the Mohs scale, earthy to vitreous luster, microcrystalline/cryptocrystalline quartz structure, brownish-yellow to tan translucent appearance due to iron oxide inclusions, conchoidal fracture.
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Physical properties
Hardness 7 on the Mohs scale, earthy to vitreous luster, microcrystalline/cryptocrystalline quartz structure, brownish-yellow to tan translucent appearance due to iron oxide inclusions, conchoidal fracture.
Formation & geological history
Formed through the precipitation of silica from groundwater in sedimentary environments, or as a river-worn pebble weathered from quartz veins and silica-rich host rocks.
Uses & applications
Commonly collected as river rocks, used in landscaping, road construction aggregate, or as general lapidary material for tumbling.
Geological facts
Small quartz and chert pebbles like this are amongst the most common rocks found in riverbeds, lakeshores, and gravel pits worldwide due to their high chemical stability and hardness.
Field identification & locations
Identify by its hardness (scratches glass), lack of cleavage, smooth stream-rounded edges, and waxy to vitreous surface appearance. Found along gravel bars, riverbeds, beaches, and glaciated terrain.
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