mineral

Polished banded agate (likely plume or moss agate)

Chalcedony, cryptocrystalline SiO₂, with iron-oxide and other mineral inclusions

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; dark brown, black, cream, and tan curved banding; waxy to vitreous luster; microcrystalline quartz with no visible cleavage; specific gravity about 2.6. The rounded, glossy surface indicates tumbling or polishing.

Identified September 10, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony in successive bands over long periods, commonly during the Cenozoic. Colors and plume-like patterns result from iron and manganese oxides or other inclusions.

Uses & applications

Used for cabochons, beads, carvings, ornamental stones, and small decorative objects; less commonly for knife-edge burnishers and industrial abrasives.

Geological facts

Agate banding is often highly distinctive, and every specimen has a unique pattern. It may be dyed, so unusually vivid or perfectly uniform colors should be treated cautiously.

Field identification & locations

Identify by its hardness, waxy polish, translucent edges, curved concentric bands, and lack of cleavage; it should scratch glass but not be scratched by a steel blade. Common sources include Brazil, Uruguay, India, Mexico, Madagascar, and the western United States.