sedimentary

Chert / Flint

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale. Color: Light grey to off-white/beige. Luster: Waxy to dull. Fracture: Distinct conchoidal fracture with sharp edges. Microcrystalline structure.

Hardness: 7 on Mohs scale
Color: Light grey to off-white/beige
Luster: Waxy to dull

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Light grey to off-white/beige. Luster: Waxy to dull. Fracture: Distinct conchoidal fracture with sharp edges. Microcrystalline structure.

Formation & geological history

Formed biogenically or chemically through the precipitation of silica-rich fluids within marine sedimentary rocks, particularly limestones and chalk deposits.

Uses & applications

Historically used for stone tools, arrowheads, and flintlock firearms due to its sharp conchoidal fracture. Used today as road aggregate and ballast.

Geological facts

Because chert breaks with smooth, sharp edges like glass, it was one of the most critical materials used by early humans to manufacture knapped stone tools.

Field identification & locations

Identified by its high hardness (scratches steel), smooth waxy feel, and characteristic curved, shell-like conchoidal fracture surfaces. Extremely common in limestone terrains worldwide.