sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 Mohs; Color: Grey, black, brown, or dull green; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline/Microcrystalline; Fracture: Conchoidal; Specific gravity: 2.65
- Hardness
- 6
- Color
- Grey, black, brown, or dull green
- Luster
- Waxy to vitreous
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 Mohs; Color: Grey, black, brown, or dull green; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline/Microcrystalline; Fracture: Conchoidal; Specific gravity: 2.65
Formation & geological history
Formed through the precipitation of silica-rich fluids within sedimentary host rocks, often as nodules or bedded layers. Usually occurs in limestone or chalk beds from Paleozoic to Cenozoic eras.
Uses & applications
Historically used for stone tools/weapons (knapping) and fire-starting. Currently used in road surfacing, grinding media, and occasionally as decorative gravel or gemstone (jasper varieties).
Geological facts
Chert was one of the first resources humans traded over long distances during the Stone Age. It breaks with a conchoidal fracture, creating razor-sharp edges.
Field identification & locations
Identify by its waxy appearance, extreme hardness (it will scratch glass), and the curved, shell-like (conchoidal) patterns on broken surfaces. Found worldwide in limestone formations.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary