sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan, grey, or yellowish-brown, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture)
Identified More sedimentary →
Explore Chert (Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or yellowish-brown, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture)
Formation & geological history
Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or by chemical precipitation in marine sedimentary environments. Found in Paleozoic to Cenozoic strata.
Uses & applications
Historically used for stone tools and starting fires. Currently used as road aggregate, architectural stone, and for lapidary work (polishing).
Geological facts
Chert has been used by humans for hundreds of thousands of years to make arrowheads and knives due to its sharp edges when broken.
Field identification & locations
Look for a very hard, smooth-textured rock that exhibits shell-like (conchoidal) fractures. Often found as nodules within limestone or as river pebbles.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary