gemstone

Tumbled agate beads

Agate, a banded microcrystalline variety of chalcedony (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent gray, blue-green, cream, and brown with concentric or irregular banding; waxy to vitreous luster. Quartz forms cryptocrystalline fibrous masses with no visible cleavage and specific gravity around 2.6.

Identified September 3, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rocks, commonly basalts; successive deposition produces bands over long geological periods, generally in Cenozoic and older volcanic terrains. These pieces are cut and polished into beads.

Uses & applications

Used for jewelry, beads, ornaments, carvings, and decorative objects; common tumbled material has modest collector value.

Geological facts

The circular patterns are cross-sections of agate banding, sometimes surrounding a hollow or crystalline center. Colors may be natural or enhanced by dyeing and heat treatment.

Field identification & locations

Identify by hardness, waxy translucence, curved/concentric banding, and resistance to scratching by steel; glass or dyed glass lacks natural fine banding and consistent quartz hardness. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.