sedimentary
Chert (Fossiliferous Chert/Flint)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.7
Identified More sedimentary →
Explore Chert (Fossiliferous Chert/Flint) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Gray to Tan, Luster: Waxy to dull, Structure: Cryptocrystalline, Fracture: Conchoidal, Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often replacing carbonate rocks. This specimen contains visible fossil inclusions, likely from the Paleozoic or Mesozoic eras.
Uses & applications
Historically used for stone tools and fire-starting. Currently used in road construction, landscaping, and as a decorative specimen for fossil collectors.
Geological facts
Chert is so hard it will scratch glass and even steel. It was highly prized by indigenous cultures for making arrowheads and scrapers due to its sharp, glass-like edges when broken.
Field identification & locations
Identify by its hardness (won't be scratched by a knife) and smooth, shell-like fracture surfaces. Often found in riverbeds or within limestone outcrops globally, especially in North America and Europe.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary