sedimentary
Chert (variant Flint)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Grayish-blue to brownish-white, waxy to dull luster, conchoidal fracture (breaks into sharp, curved edges), trigonal crystal system (microscopic).
- Hardness
- 7 on Mohs scale
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-blue to brownish-white, waxy to dull luster, conchoidal fracture (breaks into sharp, curved edges), trigonal crystal system (microscopic).
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from groundwater within sedimentary layers like limestone or chalk.
Uses & applications
Historically used for stone tools and weapons (arrowheads) due to its sharp edges. Modernly used as a jewelry gemstone, in road construction, and for flint-and-steel fire starting.
Geological facts
Flint was one of the first 'high-tech' materials for early humans; it can produce sparks when struck against steel or pyrite, which led to its use in flintlock firearms.
Field identification & locations
Identify in the field by its distinctive 'glassy' conchoidal fracture and its ability to scratch glass. Found globally in nodules within limestone or as river-worn cobbles.
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