gemstone

Banded agate cabochon

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Polished oval cabochon with pale gray-white concentric banding and translucent chalcedony; vitreous to waxy luster, no visible cleavage, Mohs hardness 6.5–7, specific gravity about 2.60–2.65. The metal setting is human-made, but the gem material is geological.

Identified September 11, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony in successive layers. Individual agates may span millions of years; the specimen’s exact age and locality cannot be determined visually.

Uses & applications

Used in rings, cabochons, beads, carvings, and decorative objects. This small, relatively plain cabochon commonly sells for about $5–$30; higher prices require exceptional pattern, color, provenance, or craftsmanship.

Geological facts

The bands reflect changing silica chemistry and impurities during growth. Agate is a variety of chalcedony, and its banding is often revealed or enhanced by polishing.

Field identification & locations

Identify by hardness, waxy/vitreous luster, translucency, and curved or parallel bands; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, and Pakistan; the Karachi-region prior is plausible, though locality cannot be confirmed from the image.