sedimentary

Chert / Flint Nodules

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: tan, grey, cream, or white; Luster: waxy to dull; Structure: microcrystalline (no visible crystals); Cleavage: none, breaks with a conchoidal (shell-like) fracture.

Hardness: 6
Color: tan, grey, cream, or white
Luster: waxy to dull

Identified March 4, 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

Formation & geological history

Formed through the replacement of limestone or chalk by silica-rich fluids. Often occurs as nodules in sedimentary deposits, particularly from the Cretaceous period (approx. 66–145 million years ago).

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include road aggregate, decorative landscaping stone, and as a component in ceramics.

Geological facts

Chert/Flint was one of the most important minerals to early humans because its conchoidal fracture allows it to be shaped into razor-sharp edges and it creates sparks when struck against steel.

Field identification & locations

Identify by its waxy texture, hardness (it will scratch glass), and the way it breaks into sharp, curved flakes. Commonly found in limestone outcrops, riverbeds, and chalk cliffs.