sedimentary
Chert (Iron-stained Flint / Jasper)
Microcrystalline Quartz (SiO2) with Iron Oxides
Hardness 6.5-7 on Mohs scale; color varies from reddish-brown, yellow-ochre to grayish tan; dull to waxy luster; microcrystalline structure; conchoidal fracture with sharp edges; specific gravity around 2.65.
Identified More sedimentary →
Explore Chert (Iron-stained Flint / Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6.5-7 on Mohs scale; color varies from reddish-brown, yellow-ochre to grayish tan; dull to waxy luster; microcrystalline structure; conchoidal fracture with sharp edges; specific gravity around 2.65.
Formation & geological history
Formed by precipitation of silica from seawater or groundwater filling voids in sedimentary rock, such as limestone or chalk. Iron oxides like goethite or hematite provide the brown and reddish coloration.
Uses & applications
Historically used for stone tools, arrowheads, and flintlock ignition systems due to its sharp conchoidal fracturing. Used today in landscaping, decorative stone collecting, and gravel.
Geological facts
Chert was one of the earliest raw materials utilized by early humans to fashion sharp tools. When struck against steel or pyrite, fine-grained chert produces sparks capable of starting a fire.
Field identification & locations
Identified by its high hardness (scratches glass easily), smooth or slightly waxy texture, lack of visible crystals, and smooth shell-like (conchoidal) fractures. Widespread worldwide in limestone and chalk deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sedimentary Sandstone
Arenite (Sedimentary Rock)
sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary