mineral
Tumbled carnelian (red-orange chalcedony)
Carnelian, a microcrystalline variety of quartz; SiO₂
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent reddish-brown to orange, with a waxy to vitreous luster and no visible cleavage. Its color commonly comes from iron oxides or hydroxides within cryptocrystalline quartz.
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Physical properties
Hardness 6.5–7 Mohs; translucent reddish-brown to orange, with a waxy to vitreous luster and no visible cleavage. Its color commonly comes from iron oxides or hydroxides within cryptocrystalline quartz.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, later incorporating iron staining; deposits range from ancient volcanic terrains to younger alluvial gravels. The specimen has been cut or tumbled and polished.
Uses & applications
Used for beads, cabochons, carvings, seals, and ornamental objects; it has modest jewelry value and is popular with mineral collectors.
Geological facts
Carnelian is closely related to sard, which is generally darker and browner. Heat treatment can intensify its orange-red color.
Field identification & locations
Identify it by its warm red-orange color, translucency, waxy polish, and lack of cleavage; glass may show bubbles or sharper conchoidal breaks. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.
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