sedimentary

Chert (Flint)

Chert (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs scale; Color: Grey, black, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 Mohs scale
Color: Grey, black, or tan
Luster: Waxy to dull

Identified July 9, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs scale; Color: Grey, black, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. These often occur as nodules within limestone or chalk beds.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and to start fires. Modern uses include road surfacing, decorative garden stones, and as a raw material for ceramics.

Geological facts

Flint is a variety of chert that occurs primarily in chalk and marly limestone. It was the most important material for early human technology due to its ability to break into razor-sharp edges.

Field identification & locations

Identified by its extremely smooth, curved (conchoidal) fracture surfaces and its ability to scratch glass. Commonly found in riverbeds, fields, and coastal chalk cliffs.