mineral

Tumbled banded agate

Microcrystalline quartz (SiO₂), chiefly chalcedony with iron-oxide bands

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7, waxy to vitreous luster, opaque to translucent, and composed of cryptocrystalline quartz without visible cleavage. This small polished specimen is cream, tan, and brown with curved banding and a smooth surface.

Identified August 26, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive chalcedony layers; the bands may develop over thousands to millions of years, commonly in Paleozoic–Cenozoic volcanic terrains.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and polished stones; durable agate is also used for small tools and decorative surfaces.

Geological facts

Concentric or curved banding is its key feature; brown coloration commonly comes from iron oxides. The specimen appears tumbled and polished rather than naturally weathered.

Field identification & locations

Identify it by hardness, curved internal bands, waxy luster, and inability to scratch it with a steel knife easily; common sources include Brazil, Uruguay, Mexico, India, and the United States.