mineral

Polished banded agate

Agate, microcrystalline quartz (SiO₂), commonly chalcedony with iron-oxide impurities

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent brown, cream, and gray concentric banding; waxy to vitreous luster when polished; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The rounded form appears tumbled or polished.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms as silica-rich groundwater fills cavities in volcanic rocks, depositing successive layers of chalcedony and quartz over time; individual agates may develop over thousands to millions of years. Common localities include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.

Uses & applications

Used for cabochons, beads, carvings, bookends, decorative spheres, and ornamental objects; durable polished agate is also used in small industrial components.

Geological facts

Banded patterns arise from changing chemistry, permeability, and iron content during repeated silica deposition. Brown-red coloration typically reflects dispersed iron oxides or hydroxides.

Field identification & locations

Identify by its fine, curved or concentric bands, translucent edges, waxy appearance, and glass-scratch hardness; it is denser and more naturally patterned than most glass imitations. This specimen is likely a polished agate sphere rather than a raw rock.