sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Gray, tan, brown, or white. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Hardness: 7 (Mohs scale), Color: Gray, tan, brown, or white
Color: Gray, tan, brown, or white
Luster: Waxy to dull

Identified June 29, 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 (Mohs scale), Color: Gray, tan, brown, or white. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Formed by the precipitation of silica in marine or groundwater environments, often replacing carbonate minerals or accumulating as siliceous oozes from marine organisms. It is found in many geological eras from Precambrian to Cenozoic.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) and fire-starting. Currently used as a gemstone (Jasper), construction aggregate, and in heavy industry as a grinding medium.

Geological facts

Flint is a variety of chert that occurs in chalk or marly limestone. It was the primary material for human survival during the Stone Age due to its ability to produce razor-sharp edges and sparks when struck against steel.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture, waxy luster, and high hardness (it will scratch glass). Often found in limestone or chalk beds and stream beds.