sedimentary
Chert (variously known as Flint)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Black, grey, translucent white; Luster: Waxy to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Black, grey, translucent white
- Luster
- Waxy to vitreous
Identified More sedimentary →
Explore Chert (variously known as Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Black, grey, translucent white; Luster: Waxy to vitreous; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic debris (like sponge spicules or radiolarians) or the chemical replacement of limestone/chalk by silica in marine environments.
Uses & applications
Historically used for stone tools and starting fires (flint); currently used in jewelry (as jasper/agate variants) and as a decorative stone or abrasive.
Geological facts
Chert was the primary material for prehistoric arrowhead and scrapers due to its predictable conchoidal fracture which creates razor-sharp edges.
Field identification & locations
Identify by its 'shell-like' curved fractures and ability to scratch glass. Commonly found as nodules in limestone beds or as pebbles in stream beds.
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