mineral

Polished agate cabochons

Agate, a banded variety of chalcedony (microcrystalline quartz, SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster; trigonal quartz structure, usually without visible cleavage. The upper stone is gray and translucent; the lower is brown with concentric bands.

Identified October 3, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; waxy to vitreous luster; trigonal quartz structure, usually without visible cleavage. The upper stone is gray and translucent; the lower is brown with concentric bands.

Formation & geological history

Agate forms as silica-rich fluids deposit successive layers in cavities, commonly in volcanic rocks. Its age varies with the host rock and may range from millions to billions of years.

Uses & applications

Polished agate is used in jewelry, ornaments, and collectibles; agate is also used for small decorative and precision objects.

Geological facts

The concentric bands record successive mineral deposition and can form striking eye-like patterns.

Field identification & locations

Look for hardness, translucent chalcedony, and curved or concentric bands; agates occur worldwide, especially in volcanic regions and river gravels. These appear shaped and polished, but their exact locality cannot be determined from the image.