sedimentary

Banded Agate (Banded Chert / Jasper)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Dark grey, reddish-brown, and tan/white banding. Luster: Vitreous to waxy. Crystal Structure: Microcrystalline/Cryptocrystalline trigonal quartz. Cleavage: None (conchoidal fracture). Specific Gravity: ~2.6.

Hardness: 6
Color: Dark grey, reddish-brown, and tan/white banding
Luster: Vitreous to waxy

Identified July 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through silica precipitation from fluids depositing layer by layer in rock cavities or sedimentary environments, often associated with Precambrian iron formations or volcanic hosts.

Uses & applications

Polished for lapidary arts, jewelry components, wire-wrapping, or collected as tumbled decorative stones.

Geological facts

Banded agates and jasper/chert variants often preserve fine depositional layers formed over thousands of years, with iron oxide impurities creating distinct reddish hues.

Field identification & locations

Look for distinct fine parallel banding or striping on a smooth, hard surface. Commonly found along beaches, riverbeds, and gravel deposits worldwide, including Lake Superior and Brazil.