sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

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

Hardness: 7 on Mohs scale
Color: Gray, tan, or white
Luster: Waxy to dull

Identified May 9, 2026More sedimentary →

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Physical properties

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

Formation & geological history

Formed from the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or through chemical precipitation in marine environments and limestone cavities.

Uses & applications

Historically used for stone tools and weapons (arrowheads). Modernly used in construction aggregate, road surfacing, and as a component in glass manufacturing.

Geological facts

Chert is so hard it can produce sparks when struck against steel, which made it essential for flintlock firearms and early fire-starting.

Field identification & locations

Identify in the field by its very smooth, shell-like (conchoidal) fracture surfaces and sharp edges. It is commonly found in limestone or chalk deposits globally.