mineral

Polished agate slice

Agate, a banded variety of chalcedony (microcrystalline SiO₂)

AI-generated identification · may be incorrect

Translucent orange, brown, gray, and white bands with a polished surface; Mohs hardness 6.5–7, vitreous to waxy luster, trigonal microcrystalline quartz, and no distinct cleavage.

Identified October 2, 2026More mineral →

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Physical properties

Translucent orange, brown, gray, and white bands with a polished surface; Mohs hardness 6.5–7, vitreous to waxy luster, trigonal microcrystalline quartz, and no distinct cleavage.

Formation & geological history

Silica-rich groundwater deposited successive chalcedony layers in a cavity, likely in volcanic rock. Agates form across many geological ages and commonly occur in volcanic regions.

Uses & applications

Used for ornaments, jewelry, bookends, and decorative slabs; valued by collectors for distinctive banding.

Geological facts

Agate bands can record changes in mineral-rich fluids as a cavity gradually fills.

Field identification & locations

Identify it by its curved, concentric bands and translucence, often best seen when backlit; common sources include Brazil, Uruguay, India, and the western United States. This appears to be a cut and polished slice.