mineral

Tumbled agate/chalcedony

Microcrystalline quartz (SiO₂), likely brown/orange agate with iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent tan, honey-brown, and gray coloration with waxy-to-glassy luster. Quartz has trigonal crystal structure, but chalcedony is cryptocrystalline and lacks visible cleavage; specific gravity is about 2.6.

Identified August 14, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers of chalcedony and quartz; iron oxides create the brown and orange colors. Individual specimens may range from Paleozoic to Cenozoic age depending on source locality.

Uses & applications

Commonly tumbled for collecting, cabochons, jewelry, ornaments, and decorative objects; agate is also used for beads and small carvings. This quality is primarily decorative rather than industrial.

Geological facts

The rounded shape and glossy surface indicate human tumbling and polishing. Translucent edges, subtle banding, and a hardness sufficient to scratch ordinary glass support an agate/chalcedony identification.

Field identification & locations

Common worldwide, especially Brazil, Uruguay, Mexico, Madagascar, India, and the western United States. Inspect under strong light for curved or concentric banding; an iron-stained jasper/chalcedony mixture is also possible.