sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs, Color: tan, grey, yellow-brown, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
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, Color: tan, grey, yellow-brown, Luster: waxy to dull, Crystal structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Forms primarily as nodules or layers in limestone or chalk through the replacement of calcium carbonate by silica-rich fluids. It can also form as primary chemical precipitates on the ocean floor.
Uses & applications
Historically used for stone tools and weapons (arrowheads). Modernly used in construction aggregate, road surfacing, and as high-quality flint for fire-starting tools.
Geological facts
Because it breaks with a conchoidal fracture like glass, it creates edges that can be sharper than a surgical scalpel. It has been used by humans for over 2 million years.
Field identification & locations
Identify in the field by its sharp, curved fracture edges and its hardness (it will scratch glass). Look for it as nodules protruding from weathered limestone outcrops.
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
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary