sedimentary

Chert (Flint)

Microcrystalline quartz (SiO2)

Hardness: 7 on Mohs scale. Color: White, grey, brown, or black. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic quartz crystals). Cleavage: None, fractures conchoidally. Specific gravity: 2.60 - 2.65.

Hardness: 7 on Mohs scale
Color: White, grey, brown, or black
Luster: Waxy to vitreous

Identified August 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the chemical precipitation of silica from aqueous solutions, often replacing carbonate rocks like limestone or chalk during diagenesis. Found globally in sedimentary sequences ranging from Precambrian to Cenozoic ages.

Uses & applications

Historically used for making stone tools, arrowheads, and firearm flints. Occasionally used as decorative landscaping gravel or tumbled stones.

Geological facts

Chert and flint are essentially the same material; 'flint' is typically used for darker varieties found in chalk formations, while 'chert' is used for lighter varieties found in limestone.

Field identification & locations

Easily identified by its conchoidal fracture (smooth, curved surfaces like broken glass) and high hardness which easily scratches glass. Common worldwide in limestone and chalk regions.