mineral

Tumbled chalcedony or carnelian

Microcrystalline quartz (SiO₂), likely iron-bearing chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange-brown to cream coloring, waxy-to-glassy luster, and no visible cleavage. The rounded, polished form indicates tumbling; reddish tones commonly come from iron oxides.

Identified August 10, 2026More mineral →

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Physical properties

Formation & geological history

Chalcedony forms when silica-rich fluids fill cavities and fractures, depositing microscopic quartz fibers, often in volcanic rocks. Its exact geological age cannot be determined from the photograph; specimens occur from many ages and regions.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and lapidary collections; durable pieces may be set in jewelry. Common tumbled specimens generally have modest value.

Geological facts

If the red-orange coloration is stronger and more uniform, the material is conventionally called carnelian; cream-brown varieties may be called orange chalcedony or sard. The image alone cannot reliably distinguish these varieties.

Field identification & locations

Common in volcanic cavities, sedimentary gravels, and stream deposits worldwide, especially Brazil, India, Madagascar, Uruguay, and the United States. Identify by its waxy appearance, translucency, lack of cleavage, and ability to scratch glass; a streak or hardness test can confirm it.