sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture with no true cleavage, colors range from grey and brown to white and black, specific gravity of 2.60 to 2.65.

Identified August 5, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture with no true cleavage, colors range from grey and brown to white and black, specific gravity of 2.60 to 2.65.

Formation & geological history

Formed through the replacement of calcium carbonate by silica in marine environments, or from the accumulation of siliceous skeletal remains of microscopic organisms such as radiolarians and diatoms, over millions of years.

Uses & applications

Historically used for making stone tools and weapons due to its sharp conchoidal fracture; currently used for decorative landscaping, road aggregate, and occasionally in abrasive products.

Geological facts

Chert is a microcrystalline or cryptocrystalline sedimentary rock. When found in chalk or limestone formations as nodules, it is commonly called flint. It was one of the earliest materials utilized by early humans for fire-starting and weaponry.

Field identification & locations

Identified easily by its distinctive conchoidal fracture (smooth, curved breakage patterns like broken glass), hard waxy surface, and ability to scratch glass easily. Commonly found globally in chalk and limestone deposits.