gemstone

Polished gray-blue agate slice pendant

Agate, a banded microcrystalline variety of chalcedony (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray, blue-gray, and white concentric banding; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The edge appears polished or possibly metal-rimmed, with a drilled/attached pendant bail.

Identified September 3, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, depositing successive layers of chalcedony and quartz. Individual bands may form over thousands to millions of years, commonly in Cenozoic volcanic terrains.

Uses & applications

Used for cabochons, pendants, beads, ornaments, and carvings; durable and attractive but generally modestly priced unless the pattern, color, and translucency are exceptional.

Geological facts

Agate banding records repeated changes in fluid chemistry, temperature, and silica saturation during cavity filling. Blue-gray coloration may be natural or enhanced by dyeing, though this specimen appears plausibly natural.

Field identification & locations

Identify by curved/concentric bands, translucent edges, quartz-like hardness, and resistance to scratching by steel; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.