sedimentary

Chert

Microcrystalline quartz (SiO2)

Hardness: 7 on the Mohs scale, Color: Light grey, white, tan, Luster: Dull to waxy, Fracture: Conchoidal, Specific Gravity: 2.60 to 2.65

Luster: Dull to waxy, Fracture: Conchoidal, Specific Gravity: 2

Identified August 6, 2026More sedimentary →

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Physical properties

Hardness: 7 on the Mohs scale, Color: Light grey, white, tan, Luster: Dull to waxy, Fracture: Conchoidal, Specific Gravity: 2.60 to 2.65

Formation & geological history

Formed via the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of marine organisms, diatoms, or radiolarians, typically in deep marine environments over millions of years.

Uses & applications

Historically used by early humans for making stone tools such as arrowheads, spear points, and blades due to its conchoidal fracture. Also used in abrasives and road metal.

Geological facts

Chert has been utilized by humans for stone tool making for over two million years. Flint is a well-known dark variety of chert often found in chalk formations.

Field identification & locations

Identified in the field by its hardness (scratches glass easily), smooth or waxy texture, and distinct conchoidal fracture pattern. Commonly found embedded in limestone or chalk deposits globally.