mineral

Polished banded agate slice

Agate, a banded variety of microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Mostly gray-brown concentric bands with a translucent white center and vitreous luster; trigonal quartz, Mohs hardness 6.5–7, no cleavage, specific gravity about 2.6. The photograph shows a cut and polished slice, so precise identification of banding and color is more reliable than judging natural surface texture.

Identified October 10, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited successive layers of chalcedony in a cavity, commonly in volcanic rock; the specimen’s age and locality cannot be determined from the image.

Uses & applications

Used for jewelry, ornaments, bookends, and lapidary display; agate is also used for small precision components and abrasives.

Geological facts

Agate’s bands record repeated changes in mineral deposition; the bright center may be a cavity or translucent chalcedony catching the light.

Field identification & locations

Identify by its curved, concentric bands and fine-grained quartz texture; agates occur worldwide, notably in Brazil, Uruguay, India, and the United States. A scratch test on an inconspicuous spot can help distinguish quartz from softer look-alikes.