mineral
Tumbled banded agate
Microcrystalline quartz (SiO₂), a variety of chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent to opaque brown, cream, and gray bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage. The image shows a small polished, rounded specimen; exact identification is uncertain from appearance alone.
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Physical properties
Hardness 6.5–7 Mohs; translucent to opaque brown, cream, and gray bands; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage. The image shows a small polished, rounded specimen; exact identification is uncertain from appearance alone.
Formation & geological history
Forms as silica-rich groundwater deposits concentric or layered chalcedony in cavities and fractures, often in volcanic rocks. Agates occur across many geological ages and settings.
Uses & applications
Commonly used for jewelry, beads, ornaments, and lapidary collecting; polished specimens are valued for their patterns.
Geological facts
Agate’s fine bands can record successive changes in silica deposition and groundwater chemistry.
Field identification & locations
Look for curved or parallel color bands and a smooth, hard surface; agate occurs worldwide, including Brazil, Uruguay, India, and the western United States. Similar-looking banded stones may require closer inspection for precise identification.
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Mineral