sedimentary

Chert (Flint variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan, beige, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan, beige, or grey
Luster: Waxy to dull

Identified May 18, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan, beige, or grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

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

Uses & applications

Historically used for stone tools and arrowheads due to its sharp edges; used today as road surfacing material and for decorative landscaping.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces razor-sharp edges. It is often referred to as 'Earth's first high-tech material.'

Field identification & locations

Look for a smooth, waxy surface and shell-like (conchoidal) fractures. It is harder than steel and will scratch glass. Commonly found in sedimentary basins and along stream beds.