gemstone

Tumbled banded agate

Microcrystalline quartz (chalcedony), SiO₂, with iron-oxide coloring

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to vitreous luster; translucent brown, cream, and reddish bands; cryptocrystalline structure with no visible cleavage, conchoidal fracture, and specific gravity about 2.6.

Identified August 23, 2026More gemstone →

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Physical properties

Hardness 6.5–7 Mohs; waxy to vitreous luster; translucent brown, cream, and reddish bands; cryptocrystalline structure with no visible cleavage, conchoidal fracture, and specific gravity about 2.6.

Formation & geological history

Forms as silica-rich groundwater fills cavities in volcanic rocks, depositing successive layers of chalcedony and quartz, often during the Cenozoic or older volcanic episodes. The specimens shown are polished/tumbled pieces.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive collectible stones; durable enough for jewelry and decorative objects.

Geological facts

The banding reflects changing fluid chemistry, iron content, and silica deposition over time. Agate is a variety of chalcedony rather than a separate mineral species.

Field identification & locations

Identify by curved or parallel color bands, waxy luster, hardness, and resistance to scratching by steel; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.