sedimentary

Chert (Flint)

SiO2 (Microcrystalline Quartz)

Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, cream with iron staining. Luster: Waxy to dull. Fracture: Conchoidal. Specific Gravity: 2.5-2.8.

Hardness: 7 on Mohs scale
Color: Tan, yellowish-brown, cream with iron staining
Luster: Waxy to dull

Identified July 25, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Tan, yellowish-brown, cream with iron staining. Luster: Waxy to dull. Fracture: Conchoidal. Specific Gravity: 2.5-2.8.

Formation & geological history

Formed in marine environment sedimentary rock layers where silica-rich fluids precipitated microcrystalline quartz, often replacing carbonates or organic materials.

Uses & applications

Historically used for making stone tools, arrowheads, and flintlock ignition systems. Today used as road aggregate, construction fill, and landscaping stone.

Geological facts

Chert breaks with a sharp, shell-like (conchoidal) fracture, which made it one of the most vital raw materials for prehistoric human technology and toolmaking worldwide.

Field identification & locations

Identified by its high hardness (scratches glass easily), waxy texture, and sharp curved edges where fractured. Very common in limestone and chalk formations worldwide.