mineral

Banded agate

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

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; brown, orange, gray, cream, and translucent colors with concentric banding; waxy to vitreous luster; cryptocrystalline structure and no cleavage. The specimen appears cut and polished, with possible druzy quartz along one edge.

Identified September 1, 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 and quartz. Individual agates may form over weeks to millions of years, commonly in Cenozoic volcanic terrains.

Uses & applications

Used for cabochons, carvings, beads, bookends, and ornamental objects; durable polished pieces are popular with collectors and jewelry makers.

Geological facts

The intricate bands record changing chemistry, water flow, and oxidation conditions during cavity filling. Iron oxides produce the warm red-brown coloration.

Field identification & locations

Identify by its curved or concentric translucent bands, waxy polish, quartz hardness, and inability to scratch glass easily. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.