sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, typically gray or brown in color, waxy luster, amorphous or cryptocrystalline structure, and conchoidal fracture with no true cleavage.
Identified More sedimentary →
Explore Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 7 on the Mohs scale, typically gray or brown in color, waxy luster, amorphous or cryptocrystalline structure, and conchoidal fracture with no true cleavage.
Formation & geological history
Formed through the chemical precipitation of silica from seawater or the replacement of limestone by silica-rich solutions over millions of years.
Uses & applications
Historically used by early humans for making stone tools and arrowheads due to its sharp conchoidal fracture, and occasionally used in landscaping or gravel.
Geological facts
Chert is extremely durable and weather-resistant, often surviving in the geological record long after surrounding limestone erodes away. Varieties like flint and jasper are well-known sub-types.
Field identification & locations
Easily identified in the field by its hard conchoidal edges and waxy appearance. Found worldwide in sedimentary sequences, particularly within chalk and limestone formations.
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