sedimentary

Chert (Chert / Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, brown, or black; Luster: Dull to waxy; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray, brown, or black
Luster: Dull to waxy

Identified March 22, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray, brown, or black; Luster: Dull to waxy; Structure: Cryptocrystalline quartz; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation in marine environments; ages range from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to sharp edges; currently used in construction aggregate, road surfacing, and as a component in glass and ceramics.

Geological facts

Dark-colored chert is often called 'flint' and was the primary material for starting fires and discharging early firearms (flintlocks) because it produces sparks when struck against steel.

Field identification & locations

Identify in the field by its hardness (will scratch glass), smooth shell-like (conchoidal) fracture surfaces, and sharp edges. Commonly found in limestone or chalk beds as nodules or layers.