sedimentary

Banded chert or agate

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Gray, cream, and brown layered bands with a waxy to dull luster; likely hardness 6.5–7 Mohs, no visible cleavage, cryptocrystalline quartz, and specific gravity about 2.6. The irregular shape appears naturally weathered or lightly polished.

Identified August 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Most likely formed when silica-rich groundwater filled cavities or replaced sediment, producing rhythmic chalcedony bands. Its precise geological age cannot be determined from the photograph; chert and agate occur from Precambrian to modern volcanic and sedimentary settings.

Uses & applications

Used for cabochons, beads, carvings, tumbling, knife edges, and ornamental objects; attractive banding gives it modest collector value.

Geological facts

The specimen may be banded chert, agate, or silicified material; distinguishing them requires examining translucency, texture, and host-rock context. Quartz-rich material commonly scratches glass but not steel easily.

Field identification & locations

Look for a glassy or waxy surface, very fine grain, conchoidal fracture, and resistance to scratching. Common sources include volcanic cavities and silica-rich sedimentary formations worldwide.