mineral

Polished banded agate (likely onyx agate) set in a ring

Microcrystalline quartz, SiO₂; chalcedony with visible banding

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; dark gray to black with pale, wavy bands and a vitreous to waxy polish. Cryptocrystalline quartz; no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Identified October 16, 2026More mineral →

Explore Polished banded agate (likely onyx agate) set in a ring in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness 6.5–7 Mohs; dark gray to black with pale, wavy bands and a vitreous to waxy polish. Cryptocrystalline quartz; no visible cleavage, conchoidal fracture; specific gravity about 2.6.

Formation & geological history

Agate forms as silica-rich fluids fill cavities in volcanic rock, depositing chalcedony in layers. The banding develops during repeated deposition; the specimen’s exact age and locality cannot be determined from the image.

Uses & applications

Agate is used for jewelry, ornaments, and decorative objects; this piece is mounted as a ring cabochon.

Geological facts

Agate is a variety of banded chalcedony, and its patterns arise from successive silica layers rather than large visible crystals.

Field identification & locations

Look for curved or irregular bands, a hard surface that resists scratching by steel, and a smooth conchoidal fracture on an unpolished edge. Common sources include Brazil, Uruguay, India, and the United States.