sedimentary
Chert / Flint Pebble
Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Brown, tan, or grey including earthy shades, Luster: Dull to waxy, Crystal structure: Hexagonal (cryptocrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Brown, tan, or grey including earthy shades, Luster: Dull to waxy, Crystal structure: Hexagonal (cryptocrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed by the accumulation of siliceous remains of organisms like diatoms or through chemical precipitation in sedimentary environments. Common in marine limestone and chalk deposits.
Uses & applications
Used historically for stone tools (knapping) due to its sharp edges; currently used in construction as road metal and in glass manufacturing or as common landscaping rocks.
Geological facts
Flint is a variety of chert that was essential to prehistoric humans for fire-starting and weapons. It breaks into razor-sharp edges which remain sharper than surgical steel.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces if broken. Found globally in riverbeds and pebble beaches.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary