sedimentary
Chert (White-Tan)
Silicon dioxide (SiO2)
Hardness: 7 (Mohs), Color: Off-white, tan, or light gray, Luster: Waxy to dull, Crystal structure: Microcrystalline (Cryptocrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Identified More sedimentary →
Explore Chert (White-Tan) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs), Color: Off-white, tan, or light gray, Luster: Waxy to dull, Crystal structure: Microcrystalline (Cryptocrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolarians or diatoms) or by chemical precipitation in marine or freshwater environments. This specimen likely dates from the Paleozoic or Mesozoic eras.
Uses & applications
Historically used for stone tools (arrowheads and scrapers) due to its sharp edges when broken. Currently used for road construction, landscaping, and sometimes for fire-starting (flint).
Geological facts
Chert is so hard it can scratch glass. It is often found as nodules or layers within limestone beds. High-quality colorful chert is known as Jasper.
Field identification & locations
Identify in the field by its very smooth, shell-like (conchoidal) fracture pattern and its inability to be scratched by a steel knife. It is extremely common globally, particularly in limestone regions.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Concretion
Septarian Concretion containing Brachiopods/Crinoids
fossil
Shale
Shale (clastic sedimentary rock)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Shale
Argillaceous sedimentary rock
sedimentary