sedimentary
Chert pebble
Microcrystalline silica (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Gray, brown, black, and tan, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Identified More sedimentary →
Explore Chert pebble 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, brown, black, and tan, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed primarily as chemical precipitates or through the replacement of limestone by silica-rich fluids. Often contains microfossils and is found in marine sedimentary layers. Age varies by location, often millions of years old.
Uses & applications
Historically used for stone tools (arrowheads, scrapers) due to conchoidal fracture. Currently used in construction aggregate, road base, and as decorative river stones.
Geological facts
Chert is essentially the same material as flint, though the name flint is usually reserved for nodules found in chalk. It was one of the first materials used by early humans for fire-starting and tool-making.
Field identification & locations
Identify by its hardness (scratches glass), waxy appearance, and smooth, curved (conchoidal) fracture surfaces. Commonly found in riverbeds, glacial tills, and limestone outcrops.
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