sedimentary
Chert (Nodule)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Brown to dark grey, Luster: Waxy to dull, Crystal structure: Cryptocrystalline (microscopic quartz), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Identified More sedimentary →
Explore Chert (Nodule) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Brown to dark grey, Luster: Waxy to dull, Crystal structure: Cryptocrystalline (microscopic quartz), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; often found as nodules within limestone or chalk beds.
Uses & applications
Historically used for stone tools and weapons due to sharp fractures; currently used for road surfacing, as grinding media, or as decorative landscaping stones.
Geological facts
Chert has a conchoidal fracture which allows it to break into very sharp edges, a property exploited by prehistoric humans to make arrowheads and scrapers.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, shell-like fracture pattern. Common in sedimentary basins worldwide.
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