sedimentary

Flint (chert) nodule

Microcrystalline quartz (SiO₂), a variety of chert

AI-generated identification · may be incorrect

Hardness about 7 Mohs; opaque gray interior with a brown weathered cortex, dull to waxy luster, and no visible crystals. Breaks with smooth, curved conchoidal fractures rather than cleavage.

Identified October 15, 2026More sedimentary →

Explore Flint (chert) nodule in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness about 7 Mohs; opaque gray interior with a brown weathered cortex, dull to waxy luster, and no visible crystals. Breaks with smooth, curved conchoidal fractures rather than cleavage.

Formation & geological history

Silica-rich chert formed by chemical or biological silica accumulation and replacement in sedimentary deposits, commonly chalk or limestone. Its exact age cannot be determined from the image.

Uses & applications

Historically used for tools, fire-starting, and flintlock ignition; today it is collected and sometimes used decoratively.

Geological facts

Flint's sharp conchoidal edges made it an important prehistoric tool material. The brown outer rind is a weathering cortex around the darker silica-rich interior.

Field identification & locations

The gray interior, pale-brown rind, and curved fracture surfaces are typical of flint. It occurs in chalk and limestone regions, notably parts of Europe and North America; this appears to be a common, unworked nodule.