mineral

Polished agate (banded chalcedony)

Agate, microcrystalline quartz (SiO₂), variety of chalcedony

AI-generated identification · may be incorrect

Typically Mohs hardness 6.5–7; translucent gray-brown with orange and pale bands, waxy to glassy luster, and no visible cleavage. Its quartz crystals are microscopic and fibrous; the specimen appears naturally banded and roughly polished or broken-edged.

Identified October 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms as silica-rich fluids deposit successive layers inside cavities, commonly in volcanic rocks. Agates occur across many geological ages; the image does not establish this specimen’s age or locality.

Uses & applications

Used for cabochons, beads, ornaments, and collectibles; agate is also used for small decorative and precision objects.

Geological facts

Distinctive curved or concentric bands form as silica layers accumulate, sometimes around a cavity or nucleus.

Field identification & locations

Look for translucent chalcedony with repeated curved bands and hardness sufficient to scratch glass; common sources include Brazil, Uruguay, India, and the western United States. The pictured piece’s exact identification and locality cannot be confirmed from the image alone.