sedimentary

Chert (Nodule)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

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 June 28, 2026More sedimentary →

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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.