sedimentary
Chert
Chert (SiO2)
Hardness: 7 Mohs scale; Color: typically gray, brown, or tan; Luster: dull to waxy; Structure: microcrystalline or cryptocrystalline; Cleavage: none, conchoidal fracture.
- Hardness
- 7 Mohs scale
- Color
- typically gray, brown, or tan
- Luster
- dull to waxy
Identified More sedimentary →
Explore Chert in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 Mohs scale; Color: typically gray, brown, or tan; Luster: dull to waxy; Structure: microcrystalline or cryptocrystalline; Cleavage: none, conchoidal fracture.
Formation & geological history
Formed in marine environments through the accumulation of siliceous remains of organisms like diatoms and radiolarians, or via chemical precipitation from silica-rich fluids.
Uses & applications
Historically used for making stone tools (flint knapping); currently used as road base, construction aggregate, and occasionally for lapidary work.
Geological facts
Chert is so hard it can scratch glass. It is often found as nodules within limestone or dolomite beds. Flint is a specific dark variety of chert.
Field identification & locations
Identified by its extreme hardness, smooth conchoidal (shell-like) fracture surfaces, and waxy texture. Extremely common in sedimentary basins worldwide.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Mudstone
Argillite / Siliciclastic sedimentary rock
sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Brown Sandstone (River Rock)
Arenite
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary