sedimentary

Chert or jasper fragment

Microcrystalline quartz (SiO₂), likely iron-stained chert/jasper

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, opaque brown to reddish-purple, dull to waxy luster, cryptocrystalline structure, and no visible cleavage; it commonly breaks with smooth conchoidal fractures. The specimen appears weathered and naturally rounded, though its exact identity cannot be confirmed from the image alone.

Identified August 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement sediment, often in limestone, volcanic, or bedded sedimentary environments; iron oxides produce the reddish-brown color. Ages range from Precambrian to recent, depending on the deposit.

Uses & applications

Used as a durable aggregate, road material, flint-like toolstone, and occasionally as cabochons or ornamental stone when brightly patterned.

Geological facts

Chert can produce sharp edges when fractured and was widely used for prehistoric knives, scrapers, and arrowheads. Jasper is the opaque, colorful variety of silica-rich chert.

Field identification & locations

Identify by its fine-grained appearance, hardness, lack of cleavage, and conchoidal fracture; it should scratch glass but not be scratched by a steel nail. Common worldwide, especially in sedimentary and volcanic terrains.