sedimentary

Chert (with nodule)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: tan, cream, with dark brown inclusion; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: tan, cream, with dark brown inclusion
Luster: waxy to dull

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: tan, cream, with dark brown inclusion; Luster: waxy to dull; Crystal structure: cryptocrystalline; Cleavage: none (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments; often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons due to its sharp edges; currently used for road surfacing, gravel, and occasionally as lapidary material for hobbyists.

Geological facts

Chert was one of the most important materials for early humans; its ability to produce a razor-sharp edge when fractured made it essential for survival. Flint is a variety of chert.

Field identification & locations

Identify by its waxy luster, extreme hardness (it will scratch glass), and smooth, curved conchoidal fractures. Common in riverbeds and limestone outcrops.