sedimentary
Chert Nodule (Flint)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness 7 Mohs, conchoidal fracture, dull to waxy luster, microcrystalline, typically dark gray or black interior with a lighter weathered cortex.
Identified More sedimentary →
Explore Chert Nodule (Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 7 Mohs, conchoidal fracture, dull to waxy luster, microcrystalline, typically dark gray or black interior with a lighter weathered cortex.
Formation & geological history
Formed through biochemical precipitation of silica from diatoms or sponge spicules within marine carbonate sediment during the Cretaceous to Tertiary periods.
Uses & applications
Historically used for prehistoric stone tools and fire-starting; currently collected or crushed for aggregate and decorative landscaping.
Geological facts
Flint was humanity's first primary technological resource, sparking the Stone Age due to its ability to flake into razor-sharp edges.
Field identification & locations
Identify by its dark, glassy silica core beneath a rough white or tan chalky cortex; commonly found eroding out of chalk or limestone cliffs.
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