sedimentary
Chert Pebble (Water-worn Quartz/Chalcedony)
Silicon Dioxide (SiO2)
Hardness 7 on the Mohs scale, waxy to dull luster, greenish-gray color with quartz veinlets, conchoidal fracture, microcrystalline structure, specific gravity ~2.65.
Identified More sedimentary →
Explore Chert Pebble (Water-worn Quartz/Chalcedony) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 7 on the Mohs scale, waxy to dull luster, greenish-gray color with quartz veinlets, conchoidal fracture, microcrystalline structure, specific gravity ~2.65.
Formation & geological history
Formed from the accumulation of siliceous oozes or chemical precipitation of silica in ocean or lake beds, followed by diagenesis, erosion, and rounding by river or beach water action.
Uses & applications
Historically used for flintknapping tools; modern uses include landscaping gravel, decorative stone, and educational rock specimens.
Geological facts
Water-rounded chert pebbles are often found on riverbeds and ocean beaches. Due to high microcrystalline quartz content, chert is highly resistant to chemical and physical weathering.
Field identification & locations
Identify by its hardness (scratches glass readily), smooth water-rounded surface, waxy luster, and lack of visible mineral grains. Commonly found on pebble beaches, gravel bars, and glacial till deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary