mineral

Tumbled chalcedony (likely brown-yellow jasper or agate)

Microcrystalline quartz (SiO₂), chalcedony variety

AI-generated identification · may be incorrect

Typically hardness 6.5–7 Mohs, waxy to vitreous luster, translucent brown, honey-yellow, and gray coloration, with no visible cleavage and conchoidal fracture. The smooth rounded surface indicates mechanical tumbling and polishing.

Identified August 19, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposited microscopic quartz fibers in volcanic cavities or sedimentary fractures; iron and other impurities produced the brown-yellow colors. Formation ages vary widely, commonly Paleozoic to Cenozoic.

Uses & applications

Used for tumbling, cabochons, carvings, beads, and ornamental objects; harder varieties are suitable for durable decorative stone. Common pieces have modest collector value.

Geological facts

The specimen may be jasper if opaque and chalcedony or agate if translucent or banded; the image does not show diagnostic banding clearly. Brown coloration commonly reflects iron oxides or hydroxides.

Field identification & locations

Commonly found in volcanic regions, alluvial gravels, and silica-rich sedimentary deposits worldwide, especially Brazil, Uruguay, India, Madagascar, and the western United States. Glassy luster, lack of cleavage, hardness, and conchoidal fracture help distinguish it from softer brown minerals.