sedimentary
Chert (Flint)
Microcrystalline Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs; Color: Brownish-black/Greyish; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 Mohs
- Color
- Brownish-black/Greyish
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs; Color: Brownish-black/Greyish; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed primarily from the accumulation of silica-rich organic remains (like radiolaria or diatoms) in marine environments, compacting over millions of years into dense rock nodules.
Uses & applications
Historically used for stone tools (arrowheads/knives) due to sharp edges; used in modern times for road surfacing, as grinding media, and for sparking fire.
Geological facts
Chert and flint were among the first materials used by early humans for tool-making. Because it breaks with a conchoidal fracture (like glass), it creates extremely sharp edges.
Field identification & locations
Identified by its waxy luster, extreme hardness (scratches glass), and shell-like (conchoidal) fracture pattern. Found in limestone or chalk deposits.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary