sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Tan, brown, white, and grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Hardness: 7 (Mohs scale)
Color: Tan, brown, white, and grey
Luster: Waxy to dull

Identified July 1, 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

Hardness: 7 (Mohs scale); Color: Tan, brown, white, and grey; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6

Formation & geological history

Formed in marine environments through the accumulation of silica-rich microfossils or chemical precipitation within limestone or chalk beds. Most specimens date from the Paleozoic or Mesozoic eras.

Uses & applications

Historically used for stone tools and weapons (arrowheads/scrapers) due to its sharp fracture edges. Today used in some construction aggregates and for striking sparks in survival kits.

Geological facts

Chert has been used by humans for over 2 million years. When struck against steel, it creates sparks, which led to the development of flintlock firearms.

Field identification & locations

Identify by its characteristic seashell-like (conchoidal) fracture pattern and its ability to scratch glass. Commonly found as nodules in sedimentary rock layers or as pebbles in riverbeds.