sedimentary
Chert
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: Brown, tan, or grey, Luster: Waxy to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), 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: Brown, tan, or grey, Luster: Waxy to dull, Crystal structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed primarily by the accumulation of siliceous remains of organisms like diatoms or radiolarians, or through chemical precipitation in shallow marine environments. Most specimens range from Precambrian to Cenozoic in age.
Uses & applications
Historically used for making stone tools (arrowheads, scrapers) and as fire-starters. Today it is used in construction aggregate and as a semi-precious stone for lapidary work.
Geological facts
Chert has a conchoidal fracture which allows it to be shaped into razor-sharp edges. It is often referred to as flint when found in chalk or marly limestone.
Field identification & locations
Identify by its extreme hardness (scratches glass) and smooth, shell-like (conchoidal) fracture surfaces. Commonly found in limestone beds or as loose nodules in riverbeds.
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