sedimentary

Chert (Flint)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, tan, or gray; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Brown, tan, or gray
Luster: Waxy to vitreous

Identified May 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and starting fires (flint and steel). Currently used in road construction, as a gemstone (jaspers), and for decorative gravel.

Geological facts

Flint is a variety of chert that was the primary material for prehistoric technology, including arrowheads and knives, because it breaks into razor-sharp edges.

Field identification & locations

Identify in the field by its smooth, waxy surface and its tendency to break into curved, shell-like (conchoidal) shapes. It will scratch glass easily.