sedimentary

Chert / Flint

Microcrystalline Quartz (SiO2)

Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, colors range from white, grey, brown to yellow and black, cryptocrystalline structure with no visible crystal faces.

Identified August 6, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, colors range from white, grey, brown to yellow and black, cryptocrystalline structure with no visible crystal faces.

Formation & geological history

Formed by the replacement of calcium carbonate by silica-rich solutions in sedimentary environments like chalk or limestone, or through the direct precipitation of silica from seawater over millions of years.

Uses & applications

Historically used for making stone tools and weapons due to its sharp conchoidal fracture; modern uses include abrasives and aggregate materials.

Geological facts

Chert and flint are chemically identical, but 'flint' typically refers to varieties found in chalk formations, while 'chert' refers to those found in limestone. It was one of the most important materials for early human technology.

Field identification & locations

Easily identified by its smooth, rounded nodules, waxy luster, and characteristic sharp conchoidal fracture surfaces. Commonly found embedded in limestone or chalk deposits worldwide.