mineral
Tumbled banded agate
Agate, microcrystalline quartz (SiO₂), a variety of chalcedony
AI-generated identification · may be incorrectPolished, rounded stone with cream-white and reddish-brown bands. Mohs hardness 6.5–7; vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, and specific gravity about 2.6.
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Physical properties
Polished, rounded stone with cream-white and reddish-brown bands. Mohs hardness 6.5–7; vitreous to waxy luster, cryptocrystalline structure, no visible cleavage, and specific gravity about 2.6.
Formation & geological history
Agate forms as silica-rich fluids deposit successive layers in cavities, commonly in volcanic rocks; its age varies with the host rock, often millions to hundreds of millions of years.
Uses & applications
Used for jewelry, ornaments, carvings, and mineral collecting; agate is also used in some precision components and abrasives.
Geological facts
The visible bands are successive chalcedony layers, and iron impurities commonly create red, brown, or orange colors.
Field identification & locations
Look for curved or roughly parallel bands and a smooth, waxy surface; common sources include Brazil, Uruguay, India, and the western United States. The photo shows a small polished specimen, but its exact source cannot be determined visually.
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