sedimentary

Chert (variations include Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Gray, tan, or brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 Mohs
Color: Gray, tan, or brown
Luster: Waxy to dull

Identified July 6, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Gray, tan, or brown; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed by the precipitation of silica from water, often replacing organic material or filling cavities in limestone/dolomite. Common in marine sedimentary environments through various geological ages.

Uses & applications

Used historically for stone tools and reaching fire (flint). Currently used as a raw material for ceramics, construction aggregate, and occasionally for lapidary work.

Geological facts

Chert was one of the most vital resources for prehistoric humans due to its ability to be chipped into sharp edges. It is extremely resistant to chemical weathering.

Field identification & locations

Identify by its waxy appearance and the sharp, curved (conchoidal) edges when broken. It will easily scratch glass and steel. Found globally in nodules or bedded layers within limestone.