sedimentary
Chert
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: light grey to green-grey, Luster: dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
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: light grey to green-grey, Luster: dull to waxy, Crystal Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.65
Formation & geological history
Formation occurs as a chemical precipitate in marine or freshwater environments, often replacing calcium carbonate in limestone or forming from silica-rich organic remains.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers). Currently used in road construction, as an abrasive, and occasionally for lapidary work.
Geological facts
Chert is essentially the same mineral as flint and jasper; flint usually refers to varieties found in chalk/limestone, while jasper is iron-stained.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by steel) and smooth, shell-like conchoidal fracture patterns. Commonly found in stream beds 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
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Quartz pebble
Silicon dioxide (SiO2)
sedimentary
Generic Pebble / Rock Fragment
Lithic fragment / Weathered rock
sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary