sedimentary

Flint (Chert variant)

Silica (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, black, or dark brown with a waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Hardness: 7 on Mohs scale
Color: Gray, black, or dark brown with a waxy luster

Identified June 28, 2026More sedimentary →

Explore Flint (Chert variant) 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: Gray, black, or dark brown with a waxy luster; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.

Formation & geological history

Formed as nodules in sedimentary rocks like chalk and limestone through the precipitation of silica from groundwater. Most specimens are from the Cretaceous or Jurassic periods.

Uses & applications

Historically used for making stone tools and starting fires (flint and steel). Currently used in road construction, ceramics, and as decorative gravel.

Geological facts

Flint was a vital resource for prehistoric humans who shaped it into arrowheads and knives. It produces sparks when struck against steel due to microscopic fragments of iron heating up fast.

Field identification & locations

Identifiable by its conchoidal (shell-like) fracture patterns and sharp edges when broken. Commonly found in coastal chalk cliffs or riverbeds across Europe and North America.