mineral
Tumbled carnelian/chalcedony
Microcrystalline quartz (SiO₂), likely iron-stained chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent honey-brown to orange with cloudy gray areas, waxy-to-glassy luster, and no visible cleavage. Its rounded shape and glossy surface indicate water-worn or mechanically tumbled chalcedony.
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Physical properties
Hardness 6.5–7 Mohs; translucent honey-brown to orange with cloudy gray areas, waxy-to-glassy luster, and no visible cleavage. Its rounded shape and glossy surface indicate water-worn or mechanically tumbled chalcedony.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, with iron oxides producing the orange-brown color; commonly associated with volcanic rocks, generally formed from Paleozoic to Cenozoic deposits. Exact age cannot be determined from the photograph.
Uses & applications
Used for beads, cabochons, carvings, and inexpensive jewelry; attractive polished pieces are popular as pocket stones and lapidary material.
Geological facts
Carnelian is the orange-red variety of chalcedony, while brown or paler material is often marketed as sard or iron-stained chalcedony. Heating can intensify its red-orange color.
Field identification & locations
Identify it by its waxy translucence, smooth conchoidal fracture, lack of cleavage, and ability to scratch ordinary glass; it should not show crystal faces. Common sources include India, Brazil, Uruguay, Madagascar, and the western United States.
