sedimentary

Chert / Flint

Silicon Dioxide (Microcrystalline Quartz, SiO2)

Hardness of 7 on the Mohs scale, colors vary from white to grey, brown, or black, waxy or vitreous luster, cryptocrystalline structure, conchoidal fracture with sharp edges, specific gravity around 2.60 to 2.65.

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed in marine environments through the chemical precipitation of silica from seawater, often replacing carbonate rocks like limestone or chalk during diagenesis. Can range widely in geological age from Precambrian to Cenozoic.

Uses & applications

Historically used extensively by ancient humans for making stone tools, arrowheads, and blades due to its conchoidal fracture. Also used for fire-starting with steel, and in modern industrial applications.

Geological facts

Chert and flint are essentially the same material, though 'flint' typically refers to varieties found in chalk or marly limestone formations, while 'chert' refers to those found in carbonate sequences.

Field identification & locations

Easily identifiable in the field by its smooth, nodular appearance, waxy luster, and distinctive conchoidal fracture that produces razor-sharp edges when struck. Found globally in limestone and chalk deposits.

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