sedimentary

Chert / Flint

Cryptocrystalline Quartz (SiO2)

Hardness: 7 on the Mohs scale. Color: Typically white, grey, beige, brown, or black. Luster: Waxy to vitreous. Crystal structure: Microcrystalline/cryptocrystalline (quartz). Cleavage: None, exhibits characteristic conchoidal fracture. Specific gravity: 2.60 to 2.65.

Hardness: 7 on the Mohs scale
Color: Typically white, grey, beige, brown, or black
Luster: Waxy to vitreous

Identified August 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the replacement of calcium carbonate by silica in sedimentary environments such as chalk or limestone formations, typically over millions of years through chemical precipitation and diagenesis.

Uses & applications

Historically used for making stone tools, arrowheads, and spark generation in firearms. Today used in decorative items, lapidary work, and occasionally as an abrasive or in construction.

Geological facts

Chert and flint are chemically identical; the term 'flint' is often used specifically for darker varieties found in chalk, while 'chert' refers to lighter varieties found in limestone.

Field identification & locations

Easily identifiable in the field by its distinct conchoidal fracture (smooth, curved shell-like breakage patterns) and high hardness which easily scratches glass. Found worldwide in sedimentary rock formations.