mineral
Tumbled chalcedony (likely brown agate)
Chalcedony, microcrystalline quartz (SiO₂); possibly agate
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; translucent brown with cloudy white patches and a waxy-to-glassy luster. Microcrystalline quartz; no visible cleavage, with conchoidal fracture. The photo alone cannot confirm agate banding.
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Physical properties
Hardness about 6.5–7 Mohs; translucent brown with cloudy white patches and a waxy-to-glassy luster. Microcrystalline quartz; no visible cleavage, with conchoidal fracture. The photo alone cannot confirm agate banding.
Formation & geological history
Silica-rich fluids deposited quartz in cavities or fractures in volcanic rocks; later weathering and tumbling rounded the pebble. The specimen’s geological age and source cannot be determined from the image.
Uses & applications
Commonly used for beads, cabochons, small carvings, and decorative or educational collections; this piece appears to be a modest tumbled specimen.
Geological facts
Agate is a patterned variety of chalcedony, but distinct concentric or parallel bands are not evident here.
Field identification & locations
Look for hardness near 7, waxy luster, translucence at thin edges, and conchoidal fracture; chalcedony occurs worldwide, often in volcanic rocks and gravels. A small tumbled piece like this typically sells for about $1–$10 USD.
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