mineral

Polished banded agate

Chalcedony (microcrystalline quartz), SiO₂

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent peach, pink, cream, and reddish bands with waxy to glassy luster. Fibrous microcrystalline quartz has no prominent cleavage and typically forms concentric or curved banding.

Identified August 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony over long periods, commonly during the Cenozoic or older volcanic episodes. The specimen is cut and polished.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and lapidary display; durable polished pieces are inexpensive jewelry materials.

Geological facts

Agate banding records changing chemistry, temperature, and flow conditions during cavity filling. The central druzy-looking area consists of tiny quartz crystals.

Field identification & locations

Identify by its curved, concentric bands, translucency, quartz hardness, and lack of cleavage; it commonly occurs in volcanic terrains worldwide, especially Brazil, Uruguay, Mexico, India, and the United States.