sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale. Color: Brownish-tan to grey, opaque. Luster: Waxy to dull. Fracture: Distinctive conchoidal fracture with sharp edges. Microcrystalline quartz structure.

Hardness: 7 on Mohs scale
Color: Brownish-tan to grey, opaque
Luster: Waxy to dull

Identified July 26, 2026More sedimentary →

Explore Chert (Flint) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale. Color: Brownish-tan to grey, opaque. Luster: Waxy to dull. Fracture: Distinctive conchoidal fracture with sharp edges. Microcrystalline quartz structure.

Formation & geological history

Formed through the accumulation of siliceous oozes or chemical precipitation of silica in marine sediment environments, often replacing limestone or chalk beds.

Uses & applications

Historically used for making stone tools, arrowheads, and flintlock firearms due to its sharp conchoidal fracture. Today used as road aggregate and ornamental specimens.

Geological facts

Chert was one of the earliest raw materials utilized by prehistoric humans to forge tools, weapons, and spark fires due to its intense hardness and predictable fracturing pattern.

Field identification & locations

Look for a microcrystalline texture, dull-to-waxy luster, high hardness (scratches glass), and characteristic curved conchoidal fractures. Extremely common in sedimentary basins worldwide.