sedimentary
Chert (River Pebble)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness 6.5-7 (Mohs), waxy to dull luster, conchoidal fracture, opaque to translucent, grey with iron-staining (yellow/brown).
Identified More sedimentary →
Explore Chert (River Pebble) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6.5-7 (Mohs), waxy to dull luster, conchoidal fracture, opaque to translucent, grey with iron-staining (yellow/brown).
Formation & geological history
Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins; rounded by water erosion in a river environment.
Uses & applications
Used historically for stone tools due to sharp edges; currently used for landscaping, road base, and occasionally as a polishing material for tumble-finish jewelry.
Geological facts
Chert is so durable that it often survives long-distance transport in rivers and glacial till while other rocks break down. It is the parent material for flint.
Field identification & locations
Identify by its waxy texture and shell-like (conchoidal) fracture lines. Commonly found in riverbeds, gravel pits, and coastal beaches.
More like this
Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary