sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 Mohs; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 Mohs
- Color
- Grey, brown, or tan
- 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; Color: Grey, brown, or tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Forms in sedimentary environments, often as nodules within limestone or chalk through the replacement of calcium carbonate by silica-rich fluids. Can be of various ages from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools (arrowheads, knives); currently used in road surfacing, as grinding media in ceramic mills, and as a starting material for fire-making (flint and steel).
Geological facts
Flint was one of the first materials exploited by early humans due to its ability to break with sharp, predictable edges. It is often found with a white 'cortex' or weathered outer rind.
Field identification & locations
Identify by its extremely sharp edges when broken, waxy texture on fresh surfaces, and smooth curved (conchoidal) fracture lines. Commonly found in riverbeds or within chalk cliffs.
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 (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary