sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Grey, brown, yellowish, and black; Luster: Waxy to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Grey, brown, yellowish, and black
Luster: Waxy to dull

Identified July 14, 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

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation within limestone or chalk beds. Most specimens can range from hundreds of millions to billions of years old.

Uses & applications

Historically used for stone tools and starting fires; currently used for lapidary work, jewelry, and archaeological study.

Geological facts

Chert has been used by humans for hundreds of thousands of years to create sharp-edged tools like arrowheads and knives due to its predictable conchoidal fracturing.

Field identification & locations

Identify in the field by its waxy texture, extreme hardness (scratches glass), and shell-like (conchoidal) fracture patterns. Often found as nodules within limestone or along riverbeds.