sedimentary
Chert (Flint)
Chert (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: Gray, black, or brown; Luster: Waxy or dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.5-2.8.
- Hardness
- 6
- Color
- Gray, black, or brown
- Luster
- Waxy or dull
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: 6.5-7 Mohs; Color: Gray, black, or brown; Luster: Waxy or dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.5-2.8.
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like sponges or radiolarians) or chemical precipitation in sedimentary basins; primarily found in limestone or chalk beds.
Uses & applications
Historically used for making stone tools (arrowheads, knives); currently used in road construction, and occasionally in jewelry as cabochons.
Geological facts
Flint was a vital resource for prehistoric humans because its conchoidal fracture produces extremely sharp edges. It can also produce sparks when struck against steel.
Field identification & locations
Look for a microcrystalline texture, conchoidal (shell-like) fractures, and a hardness that can scratch glass. Common in chalk formations or coastal gravels.
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