sedimentary

Chert (Flint Nodules)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Grey, brown, black; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: None.

Hardness: 6
Color: Grey, brown, black
Luster: Waxy to dull

Identified June 23, 2026More sedimentary →

Explore Chert (Flint Nodules) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 6.5-7 (Mohs); Color: Grey, brown, black; Luster: Waxy to dull; Structure: Cryptocrystalline; Fracture: Conchoidal (shell-like curves); Cleavage: None.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or sponges) within limestone or chalk beds. Often occurs as nodules or beds in sedimentary strata dating from Precambrian to modern times.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Modernly used in road construction, as striking stones for flintlock mechanisms, and as decorative gravel.

Geological facts

Flint is a variety of chert that specifically forms in chalk or marly limestone. It was the primary material used during the Stone Age for creating sharp cutting edges.

Field identification & locations

Identify in the field by its sharp, curved edges when broken and its ability to scratch glass. Found globally in areas with sedimentary limestone deposits, such as the White Cliffs of Dover.