sedimentary

Chert (Flint)

Silicon dioxide (SiO2)

Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture with sharp edges, microcrystalline or cryptocrystalline quartz structure, colors range from grey, white, brown to black.

Identified August 6, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture with sharp edges, microcrystalline or cryptocrystalline quartz structure, colors range from grey, white, brown to black.

Formation & geological history

Forms via the chemical or biochemical precipitation of silica from aqueous solutions, often replacing calcium carbonate in limestone or chalk formations over geological time.

Uses & applications

Historically used for making stone tools and weapons due to its sharp conchoidal fracture; currently used in aggregate, abrasive products, and sometimes lapidary or decorative purposes.

Geological facts

Chert and flint are essentially the same material; the term 'flint' is commonly used for varieties found in chalk, while 'chert' is used for varieties found in limestone.

Field identification & locations

Easily identified by its hardness, smooth waxy appearance on freshly broken surfaces, and distinct conchoidal fracture. Found worldwide in sedimentary rock sequences.