sedimentary

Chert / Flint

Chert (SiO2)

Hardness: 7 on Mohs scale; Color: Tan, brown, or light yellow; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Tan, brown, or light yellow
Luster: Dull to waxy

Identified May 24, 2026More sedimentary →

Identify your own rocks.

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

App Store Google Play

Physical properties

Hardness: 7 on Mohs scale; Color: Tan, brown, or light yellow; Luster: Dull to waxy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary basins. Often occurs as nodules in limestone or chalk.

Uses & applications

Historically used for stone tools due to sharp edges; currently used for construction aggregate, decorative landscaping, and occasionally lapidary art.

Geological facts

Flint is a variety of chert. It was one of the most important minerals for early humans, used to create arrowheads, scrapers, and to start fires.

Field identification & locations

Identified by its extremely sharp, curved (conchoidal) edges when broken and its ability to scratch glass. Found worldwide, particularly in riverbeds and limestone outcrops.