mineral
Tumbled carnelian (likely)
Chalcedony, microcrystalline quartz (SiO₂), iron-oxide colored variety
AI-generated identification · may be incorrectSmooth, polished reddish-brown to orange pebble with translucent edges and glassy/waxy luster; hardness about 6.5–7 Mohs, no visible cleavage, trigonal quartz structure, specific gravity about 2.6.
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Physical properties
Smooth, polished reddish-brown to orange pebble with translucent edges and glassy/waxy luster; hardness about 6.5–7 Mohs, no visible cleavage, trigonal quartz structure, specific gravity about 2.6.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, with iron impurities producing the red-brown color; commonly Cenozoic to older volcanic or sedimentary settings. Tumbled shape is human-processed.
Uses & applications
Used for beads, cabochons, carvings, ornamental objects, and inexpensive jewelry; historically valued as a seal stone.
Geological facts
Carnelian grades from orange-red to deep brown, and heating can intensify or alter its color. Similar material may be called sard when darker brown.
Field identification & locations
Identify by its waxy luster, hardness, lack of cleavage, translucency, and resistance to scratching by steel; common sources include India, Brazil, Uruguay, Madagascar, and the United States.
