sedimentary
Chert (Cloudy Gray)
Silicon dioxide (SiO2) - Microcrystalline Quartz
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Smoky gray with tan inclusions, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
Identified More sedimentary →
Explore Chert (Cloudy Gray) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Smoky gray with tan inclusions, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; commonly found in limestone or dolomite beds.
Uses & applications
Used historically for stone tools due to sharp edges; currently used as construction aggregate, road base, and by flint-knappers for primitive technology crafts.
Geological facts
Chert has been used by humans for hundreds of thousands of years to create arrowheads and knives because it breaks into razor-sharp edges.
Field identification & locations
Identify by its waxy appearance, extreme hardness (it will scratch glass), and its characteristic shell-like (conchoidal) fracture pattern when broken.
More like this
Other sedimentary specimens
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary