sedimentary
Chert (Nodule)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs scale); Color: Gray, brown, and tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 (Mohs scale)
- Color
- Gray, brown, and tan
- Luster
- Waxy to dull
Identified More sedimentary →
Explore Chert (Nodule) 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, brown, and tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments; typically Paleozoic to Cenozoic in age.
Uses & applications
Abrasives, historical tool-making (arrowheads/scrapers), decorative landscaping, and as a raw material for glass in some contexts.
Geological facts
Chert has been used by humans for millions of years to create sparks for fire and sharp edges for hunting tools. It is extremely resistant to weathering.
Field identification & locations
Identify in the field by its very smooth, shell-like (conchoidal) fracture and its ability to scratch glass. Often found as nodules within limestone or dolomite beds.
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
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary