sedimentary
Chert (Red Jasper)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 7 Mohs, Color: Reddish-brown (due to iron oxides), Luster: Dull to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture)
Identified More sedimentary →
Explore Chert (Red Jasper) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs, Color: Reddish-brown (due to iron oxides), Luster: Dull to waxy, Crystal Structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture)
Formation & geological history
Formed in deep-water sedimentary environments from the accumulation of siliceous remains of microscopic organisms like radiolaria or through chemical precipitation in hydrothermal veins.
Uses & applications
Historically used for making stone tools (arrowheads). Modern uses include jewelry (lapidary), decorative stones, and as an abrasive in some industrial processes.
Geological facts
Chert is one of the hardest commonly found sedimentary rocks and can strike sparks against steel. Red varieties are often called Jasper when they are opaque and rich in iron.
Field identification & locations
Identify by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass easily. Found globally in limestone beds or as nodules in river beds.
More like this
Other sedimentary specimens
Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary