sedimentary

Chert (Flint)

Chert (Cryptocrystalline silicon dioxide, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Grey, tan, brown with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 Mohs
Color: Grey, tan, brown with waxy luster

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Grey, tan, brown with waxy luster; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Forms from the accumulation of siliceous remains of marine organisms or through chemical precipitation in sedimentary environments. Can be found in limestone or chalk beds.

Uses & applications

Historically used for stone tools and starting fires; currently used in construction aggregate, road surfacing, and as a decorative stone.

Geological facts

Flint was the primary material for prehistoric toolmaking because it fractures into extremely sharp edges. It is a variety of chert commonly associated with chalk or marly limestone.

Field identification & locations

Identify by its waxy luster, smooth conchoidal (shell-like) fracture, and the fact that it can scratch glass. Common in river beds and sedimentary outcrops.