sedimentary
Flint / Chert
Silicon dioxide (SiO2)
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, opaque to translucent, colors range from grey, white, brown, to reddish-brown due to impurities.
Identified More sedimentary →
Explore Flint / Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture, opaque to translucent, colors range from grey, white, brown, to reddish-brown due to impurities.
Formation & geological history
Formed diagenetically as nodules or concretionary masses in sedimentary rock, such as chalk or limestone, through the replacement of calcium carbonate by silica-rich solutions during the Cretaceous period and other geological epochs.
Uses & applications
Historically used for making stone tools, weapons, and fire-starting (strike-a-light). Currently used in decorative landscaping, road construction, and abrasive grit.
Geological facts
Flint is a hard, tough variety of microcrystalline quartz. Prehistoric humans heavily favored it for knapping sharp-edged tools due to its predictable conchoidal fracture.
Field identification & locations
Easily identified by its conchoidal fracture, waxy luster, and ability to scratch glass (hardness 7). Commonly found weathered out of chalk cliffs along coastlines and riverbeds.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Banded Siltstone / Mudstone Pebble
Siltstone / Argillite
sedimentary