sedimentary

Flint

Microcrystalline quartz (SiO2)

Hardness of 7 on the Mohs scale, color typically dark grey, black, or brown, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with very sharp edges.

Identified July 30, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, color typically dark grey, black, or brown, waxy to vitreous luster, cryptocrystalline structure, conchoidal fracture with very sharp edges.

Formation & geological history

Formed as nodules in sedimentary rocks such as chalk and marine limestones through the replacement of calcium carbonate by silica-rich solutions over millions of years.

Uses & applications

Historically used for making stone tools, arrowheads, and blades due to its conchoidal fracture; also used for striking fire.

Geological facts

Flint and chert are essentially the same material, though 'flint' usually refers to the darker varieties found in chalk formations. It was one of the earliest materials manipulated by early humans for weaponry and tools.

Field identification & locations

Easily identified by its distinctive conchoidal fracture, dark color, waxy luster, and ability to scratch glass. Commonly found embedded in limestone or chalk cliffs globally.