sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Gray, black, or tan; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Hardness: 6
Color: Gray, black, or tan
Luster: Waxy to dull

Identified July 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Gray, black, or tan; Luster: Waxy to dull; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal; Specific Gravity: 2.6

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. Found in limestone and chalk formations across various geological eras.

Uses & applications

Historically used for stone tools and weapons (arrowheads); used today as drainage rock, in road construction, and as strike-stones for fire making.

Geological facts

Chert was one of the first materials used by early humans due to its ability to fracture with extremely sharp edges. It is often found as nodules or layers within sedimentary rock beds.

Field identification & locations

Identify by its waxy texture, inability to be scratched by a steel nail, and characteristic shell-like (conchoidal) fractures. Found worldwide in sedimentary basins.