mineral

Tumbled banded agate

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

AI-generated identification · may be incorrect

Usually Mohs hardness 6.5–7, waxy to vitreous luster, and curved or concentric reddish-brown, cream, or gray banding. It has cryptocrystalline structure, no visible cleavage, and specific gravity near 2.6.

Identified September 3, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in successive layers; the specimen shown is polished or tumbled. Formation ages vary widely, commonly Paleozoic to Cenozoic.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and lapidary pieces; durable aggregate-grade agate has minor industrial uses.

Geological facts

Its bands record repeated changes in groundwater chemistry and silica supply. Iron oxides commonly produce the warm brown and red colors visible here.

Field identification & locations

Identify it by hardness, waxy polish, translucent edges, and curved internal banding; it commonly occurs in volcanic terrains worldwide, including Brazil, Uruguay, Mexico, India, and the United States.