sedimentary

Chert (often called Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray to blue-gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Gray to blue-gray
Luster: Waxy to dull

Identified June 8, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray to blue-gray; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed in marine environments through the accumulation of silica-rich organic remains or chemical precipitation. Primary occurrence is within limestone or chalk beds.

Uses & applications

Historically used for stone tools and starting fires; currently used for decorative stone, road surfacing, and as a preferred material for arrowheads and knapping.

Geological facts

Chert is so hard it can scratch steel. When broken, it creates exceptionally sharp edges, which led to its widespread use in the Stone Age for tools and weapons.

Field identification & locations

Identify by its 'conchoidal' (shell-like) fracture pattern and its ability to scratch glass. Found globally, especially in areas with ancient limestone deposits.