sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray with yellow/tan band; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Gray with yellow/tan band
Luster: Waxy to dull

Identified June 9, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Gray with yellow/tan band; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific gravity: 2.6-2.7

Formation & geological history

Formed by the accumulation of siliceous remains of microscopic organisms (like diatoms or radiolarians) or through chemical precipitation in sedimentary environments. Common in marine limestone formations.

Uses & applications

Historically used for stone tools and arrowheads; currently used as aquarium gravel, road construction aggregate, or tumbled for lapidary jewelry.

Geological facts

Because it breaks with a conchoidal fracture, it creates edges sharper than a surgeon's scalpel. Flint is a common name for the dark varieties of chert.

Field identification & locations

Identify in the field by its hardness (it should scratch glass) and its smooth, curved (conchoidal) fracture surfaces. Commonly found in stream beds or weathering out of limestone.