sedimentary
Chert (Flint)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan, brown, or brownish-gray, Luster: waxy to dull, Structure: microcrystalline, Fracture: conchoidal (shell-like), Cleavage: none.
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, brown, or brownish-gray, Luster: waxy to dull, Structure: microcrystalline, Fracture: conchoidal (shell-like), Cleavage: none.
Formation & geological history
Formed via the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in sedimentary environments. Common in limestone deposits as nodules.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a component in ceramics. Significant in historical fire-starting.
Geological facts
Because it breaks with a conchoidal fracture creating sharp edges, it was the primary material for prehistoric tool-making. It produces sparks when struck against steel.
Field identification & locations
Identify by its characteristic smooth, curved (conchoidal) fracture surfaces and its ability to scratch glass. Widely found in riverbeds, fields, and gravel pits globally.
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