sedimentary
Chert
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale); Color: Gray to brown; Luster: Waxy to dull; Fracture: Conchoidal; Structure: Microcrystalline; Specific Gravity: 2.6-2.7.
- Hardness
- 7 (Mohs scale)
- Color
- Gray to brown
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Gray to brown; Luster: Waxy to dull; Fracture: Conchoidal; Structure: Microcrystalline; Specific Gravity: 2.6-2.7.
Formation & geological history
Formed by the precipitation of silica from aqueous solutions, often as nodules in limestone or chalk, or as bedded deposits from the accumulation of siliceous organic remains like diatoms or radiolarians.
Uses & applications
Used in ancient times for stone tools (knapping) due to its sharp edges; used today as road surfacing material and in jewelry as decorative stones.
Geological facts
Chert and its variety, flint, were among the most important materials for early humans to create spearheads and arrowheads. It can spark when struck against steel.
Field identification & locations
Identify by its smooth, waxy surface and shell-shaped (conchoidal) fractures. It is commonly found in sedimentary basins and limestone outcrops worldwide.
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