sedimentary

Chert (Flint/Jasper variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: typically brown, gray, or tan; Luster: waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: none (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: typically brown, gray, or tan
Luster: waxy to dull

Identified June 3, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: typically brown, gray, or tan; Luster: waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: none (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed by the accumulation of siliceous remains of marine organisms (diatoms, radiolarians) or by chemical precipitation from silica-rich fluids in sedimentary basins. Often found as nodules in limestone or chalk.

Uses & applications

Historically used for stone tools and starting fires (flint). Currently used in road surfacing, as grinding media, and occasionally in jewelry as lapidary material.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture produces extremely sharp edges, ideal for arrowheads and scrapers.

Field identification & locations

Identify by its waxy appearance, extreme hardness (it will scratch glass), and its tendency to break with smooth, curved surfaces (conchoidal fracture). Common in areas with limestone bedrock.