sedimentary

Flint / Chert

Silicon Dioxide (SiO2)

Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture with extremely sharp edges, opaque to translucent, colors range from black, dark brown, to grey and honey-yellow.

Identified August 3, 2026More sedimentary →

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Physical properties

Hardness of 7 on the Mohs scale, waxy or vitreous luster, conchoidal fracture with extremely sharp edges, opaque to translucent, colors range from black, dark brown, to grey and honey-yellow.

Formation & geological history

Formed diagenetically through the replacement of calcium carbonate in limestone or chalk by silica-rich solutions, typically in marine environments over millions of years.

Uses & applications

Historically used for prehistoric stone tools, arrowheads, and striking fire; currently used in decorative landscaping, abrasive grits, and ball mills.

Geological facts

Flint is a form of chert. Because of its conchoidal fracture, it breaks into razor-sharp flakes, making it one of the most important materials for early human technological development.

Field identification & locations

Found worldwide in chalk and limestone formations, often discovered as nodules weathering out of cliffs or along beaches and riverbeds. Identified by its waxy luster, hardness, and sharp conchoidal edges.