sedimentary

Chert

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: typically gray, brown, or tan; Luster: dull to waxy; Crystal structure: cryptocrystalline (microscopic quartz); Cleavage: none (conchoidal fracture); Specific gravity: 2.5-2.8.

Hardness: 7 Mohs scale
Color: typically gray, brown, or tan
Luster: dull to waxy

Identified June 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine or freshwater environments as a chemical precipitate or through the accumulation of siliceous biological microfossils like diatoms and radiolarians.

Uses & applications

Historically used for stone tools and weapons. Today used as road aggregate, architectural stone, and as a component in certain pottery and ceramics.

Geological facts

Flint is a variety of chert. It was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges for hunting tools.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy luster, and shell-like (conchoidal) fracture pattern. Found globally in limestone formations or as river gravel.