sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale; Color: Gray, tan, or white with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Gray, tan, or white with waxy luster
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 on Mohs scale; Color: Gray, tan, or white with waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and starting fires (sparking). Modern uses include road surfacing, abrasives, and as a component in jewelry (jasper/agate varieties).
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for arrowheads and scrapers.
Field identification & locations
Identify by its waxy appearance, extreme hardness (scratches glass), and shell-like (conchoidal) breakage patterns. Found globally in sedimentary basins.
More like this
Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary