sedimentary

Banded chert or agate pebble

Microcrystalline quartz (SiO₂), likely chalcedony/chert

AI-generated identification · may be incorrect

Gray, cream, and brown wavy bands with a dull-to-waxy luster; hardness about 6.5–7 Mohs, conchoidal fracture, cryptocrystalline structure, and no visible cleavage. The rounded form suggests natural abrasion or tumbling.

Identified August 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Likely formed when silica-rich fluids replaced or filled cavities and fractures in volcanic or sedimentary rock, producing layered chalcedony or chert. The specimen’s precise age and locality cannot be determined from the photograph.

Uses & applications

Used as a decorative stone, cabochon, bead, or collected as a lapidary specimen; chert is also useful for sharp-edged tools. Its small size and muted pattern give it modest commercial value.

Geological facts

The banding may reflect successive silica deposition or replacement of layered material; similar pieces are often sold as banded chert, zebra chert, or agate depending on translucency and pattern.

Field identification & locations

Check for a glassy or waxy surface, conchoidal fracture, and inability to scratch it with a steel knife; quartz should scratch ordinary glass. Common in gravel beds, volcanic terrains, and sedimentary formations worldwide.