mineral

Banded agate pebble

Microcrystalline quartz (SiO₂), chiefly chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; tan, brown, and cream parallel banding; waxy to dull luster; cryptocrystalline structure with no visible cleavage; specific gravity about 2.6. The smoothly rounded shape indicates natural water wear or tumbling.

Identified September 6, 2026More mineral →

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Physical properties

Formation & geological history

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

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and polished specimens; durable agate is also used for some industrial bearings and mortars.

Geological facts

Its banding results from changing impurities, fluid chemistry, and growth conditions during deposition. The specimen may also be a naturally banded jasper or chalcedony pebble; a close view or translucency test would refine identification.

Field identification & locations

Common in volcanic regions, river gravels, and beaches worldwide, especially Brazil, Uruguay, Mexico, India, and the western United States. Confirm with hardness, waxy luster, curved banding, and lack of fizz in dilute acid.