mineral

Polished agate slice

Banded chalcedony, microcrystalline SiO₂

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; gray, blue-green, and brown concentric bands with a waxy-to-vitreous polish. Trigonal quartz microcrystals; no visible cleavage, typically specific gravity 2.6.

Identified September 26, 2026More mineral →

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Physical properties

Mohs hardness 6.5–7; gray, blue-green, and brown concentric bands with a waxy-to-vitreous polish. Trigonal quartz microcrystals; no visible cleavage, typically specific gravity 2.6.

Formation & geological history

Silica-rich groundwater deposited successive layers inside a cavity, later solidifying into banded chalcedony. Agates form in many geological ages, commonly in volcanic rocks.

Uses & applications

Used for jewelry, decorative slabs, bookends, and collectibles; thin slices are often polished and mounted.

Geological facts

The bull’s-eye pattern is concentric agate banding; the rough outer edge is likely the original cavity wall or rind.

Field identification & locations

Agate is found worldwide, including Brazil, Uruguay, India, and the United States. Identify it by translucent silica, curved bands, and hardness sufficient to scratch glass; this image alone cannot establish its exact locality.