mineral
Polished agate slice
Agate, a banded variety of chalcedony (microcrystalline SiO₂)
AI-generated identification · may be incorrectMostly gray, cream, and brown concentric bands with a polished, waxy-to-glassy luster. Mohs hardness 6.5–7; trigonal silica in microscopic crystals, with no visible cleavage. The bright circular spot appears to be glare or a reflection.
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Physical properties
Mostly gray, cream, and brown concentric bands with a polished, waxy-to-glassy luster. Mohs hardness 6.5–7; trigonal silica in microscopic crystals, with no visible cleavage. The bright circular spot appears to be glare or a reflection.
Formation & geological history
Forms as silica-rich fluids deposit layers in cavities, commonly in volcanic rocks; banding develops through repeated deposition. Agates form across many geological ages.
Uses & applications
Used for jewelry, ornaments, polished slices, and small decorative objects; also collected as a lapidary specimen.
Geological facts
Agate’s fine silica crystals create bands that may be invisible until a nodule is cut and polished.
Field identification & locations
Identify by curved or concentric bands and hardness near 7; common sources include Brazil, Uruguay, India, and the western United States. This appears to be a cut and polished nodule slice.
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