sedimentary

Chert (varieties include Flint and Jasper)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale); Color: Variegated beige, tan, and gray; Luster: Dull to waxy; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: Variegated beige, tan, and gray
Luster: Dull to waxy

Identified March 15, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: Variegated beige, tan, and gray; Luster: Dull to waxy; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed from the accumulation of silica-rich organic remains such as radiolaria or diatoms on the seafloor, or through chemical precipitation in limestone. Can range from Precambrian to modern in age.

Uses & applications

Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a raw material for fire-starting strikers.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture creates razor-sharp edges. It is famous for being used as flint in lighters and early firearms.

Field identification & locations

Identify in the field by its extreme hardness (scratches glass) and smooth, curved shell-like (conchoidal) fracture pattern. Commonly found in riverbeds, limestone outcrops, and coastal cliffs.