sedimentary

Tumbled banded chert or jasper

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; dark reddish-brown to black with curved rusty bands, opaque, and glassy to waxy luster. It has cryptocrystalline quartz with no visible cleavage and typically high toughness after tumbling.

Identified August 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms when silica-rich fluids replace or cement fine sediment, with iron oxides producing the red-brown banding; age depends on locality and may range from Precambrian to younger. The rounded shape indicates natural water abrasion or mechanical tumbling.

Uses & applications

Used as a lapidary material for cabochons, beads, carvings, and decorative stones; attractive pieces are collected but have limited industrial value.

Geological facts

The specimen is most consistent with banded jasper or chert, though exact identification requires locality or testing. A steel file should not scratch it, while quartz or a hardened steel point may scratch its surface.

Field identification & locations

Common in gravel beds, river deposits, and jasper-bearing regions worldwide, including the western United States, Australia, and parts of India. Look for opaque silica, waxy luster, red-brown iron staining, and conchoidal fracture.