sedimentary

Chert (Flint)

Chert (Microcrystalline or cryptocrystalline Silica, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, gray; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.

Hardness: 6
Color: Brown, tan, gray
Luster: Waxy to dull

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, gray; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65.

Formation & geological history

Formed primarily from the precipitation of silica in sedimentary environments, often from the remains of siliceous organisms like diatoms or radiolaria, or through chemical replacement in limestone.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges. Modernly used in road construction, as jewelry (jasper), and as a component in flintlock firearms.

Geological facts

Chert is so hard it can strike sparks from steel. It has been used by humans for hundreds of thousands of years to create arrowheads and scrapers.

Field identification & locations

Identified in the field by its smooth, waxy surface and its tendency to break into sharp, curved (conchoidal) flakes. Common in river beds and limestone outcrops.