sedimentary
Chert (Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 Mohs scale; Color: typically grey, brown, or black; Luster: waxy to dull; Crystal structure: hexagonal (microscopic); Cleavage: none, exhibits conchoidal fracture (shell-like curves)
- Hardness
- 7 Mohs scale
- Color
- typically grey, brown, or black
- Luster
- waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs scale; Color: typically grey, brown, or black; Luster: waxy to dull; Crystal structure: hexagonal (microscopic); Cleavage: none, exhibits conchoidal fracture (shell-like curves)
Formation & geological history
Formed by the precipitation of silica from seawater or the accumulation of silica-rich organic remains (like radiolarians or diatoms) in marine environments. It can occur in all geological ages from Precambrian to Holocene.
Uses & applications
Historically used for making stone tools and weaponry due to its sharpness when fractured; currently used in construction as road aggregate, and as a component in glass and ceramics. Historically used as a spark generator in flintlock firearms.
Geological facts
Flint is a form of chert that was highly valued by prehistoric humans for its ability to be knapped into sharp edges. It is often found as nodules inside limestone or chalk formations.
Field identification & locations
Identify in the field by its very hard surface (scratches glass), waxy feel, and characteristic shell-like (conchoidal) fracture pattern. Found globally in areas with sedimentary limestone or chalk deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary