sedimentary

Chert (flint)

Microcrystalline quartz, SiO₂ (chalcedony/quartz)

AI-generated identification · may be incorrect

Gray-white, waxy to dull luster, hardness about 7 Mohs; very fine-grained with no visible crystals or cleavage, and typically breaks with curved, sharp conchoidal fractures. The image’s pale, chipped specimen is consistent with chert, though identification from a photo is uncertain.

Identified October 15, 2026More sedimentary →

Explore Chert (flint) 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

Forms when silica-rich material accumulates and hardens, often replacing carbonate sediments; deposits range from ancient to geologically recent. Chert commonly occurs as nodules or layers in limestone and chalk.

Uses & applications

Used historically for tools and fire-starting; today it is collected and occasionally used as decorative stone or aggregate.

Geological facts

Flint is a dark, compact variety of chert; sharp flakes made it valuable for prehistoric cutting tools.

Field identification & locations

Look for a very fine texture, hard surface, and curved fracture edges; common in sedimentary terrains worldwide, especially limestone and chalk regions. Avoid confusing it with glassy slag or quartz.