mineral

Polished blue banded agate slice

Chalcedony (microcrystalline quartz), SiO₂, commonly with trace iron and other coloring elements

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent to opaque blue-and-white concentric banding, vitreous to waxy luster, cryptocrystalline structure, no cleavage, and specific gravity about 2.6. The glossy face is human-polished, with a natural rough rim.

Identified August 8, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills gas cavities in volcanic rocks, depositing successive layers of chalcedony over long periods. Individual bands may form over thousands to millions of years; major deposits occur in Brazil, Uruguay, Mexico, India, and the United States.

Uses & applications

Used for cabochons, jewelry, ornaments, bookends, slabs, and decorative objects; its durability makes it suitable for carvings and polished display pieces.

Geological facts

Blue coloration may be natural but is often enhanced by dyeing, especially in vivid commercial slices. Banded agate is a variety of chalcedony rather than a separate mineral species.

Field identification & locations

Identify by curved/concentric bands, waxy translucency, quartz-like hardness, and lack of cleavage; it should resist scratching by steel but not by quartz. Commonly sold as Brazilian or Uruguayan agate slices.