mineral
Tumbled carnelian (orange chalcedony)
Carnelian, a microcrystalline quartz variety; SiO₂, commonly colored by dispersed iron oxides
AI-generated identification · may be incorrectTypically translucent orange to reddish-brown with waxy-to-glassy luster and no visible crystals; quartz hardness is Mohs 7, specific gravity about 2.6, with conchoidal fracture and no cleavage. The smooth rounded shape indicates mechanical tumbling and polishing.
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Physical properties
Typically translucent orange to reddish-brown with waxy-to-glassy luster and no visible crystals; quartz hardness is Mohs 7, specific gravity about 2.6, with conchoidal fracture and no cleavage. The smooth rounded shape indicates mechanical tumbling and polishing.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, later incorporating iron and developing orange-red color through oxidation. Deposits occur in volcanic and sedimentary terrains, generally from relatively young to ancient geological settings.
Uses & applications
Used for beads, cabochons, ornaments, and inexpensive jewelry; polished pieces are also collected as lapidary specimens.
Geological facts
Carnelian is a variety of chalcedony, itself a cryptocrystalline form of quartz. More intense red-orange color and translucency generally increase desirability.
Field identification & locations
Identify by its warm orange color, translucency, waxy polish, hardness, and lack of cleavage; common sources include India, Brazil, Uruguay, Madagascar, and Germany. A scratch test should be avoided on polished specimens.
