sedimentary

Chert (Chalky Flint Node)

Chert (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: White/cream weathered exterior, often brown or grey interior; Luster: Dull to waxy; Crystal structure: Trigonal/Cryptocrystalline; Conchoidal fracture.

Hardness: 7 Mohs
Color: White/cream weathered exterior, often brown or grey interior
Luster: Dull to waxy

Identified June 17, 2026More sedimentary →

Explore Chert (Chalky Flint Node) 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; Color: White/cream weathered exterior, often brown or grey interior; Luster: Dull to waxy; Crystal structure: Trigonal/Cryptocrystalline; Conchoidal fracture.

Formation & geological history

Formed through the chemical precipitation of silica in sedimentary environments, often replacing carbonate material in chalk or limestone beds. Common in Cretaceous and Jurrasic deposits.

Uses & applications

Historically used for stone tools and weapons (flint-knapping); currently used in road construction, as decorative gravel, and occasionally for fire-starting.

Geological facts

Flint was the primary resource for humanity's early technology, used to create the sharpest blades and first man-made fires by striking against iron pyrite.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) breakage pattern. Found globally in limestone/chalk outcrops or river beds.