sedimentary
Chert (River Pebble)
Cryptocrystalline Quartz (SiO2)
Hardness 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
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary