mineral
Yellow-orange chalcedony (possibly carnelian)
Microcrystalline quartz, SiO₂; orange coloration commonly from iron oxides
AI-generated identification · may be incorrectMohs hardness 6.5–7; translucent orange-yellow body with waxy to dull luster, conchoidal fracture, and no cleavage. It is cryptocrystalline quartz, so individual crystals are not visible.
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Physical properties
Mohs hardness 6.5–7; translucent orange-yellow body with waxy to dull luster, conchoidal fracture, and no cleavage. It is cryptocrystalline quartz, so individual crystals are not visible.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, followed by slow quartz precipitation; iron produces the orange color. Typically Cenozoic to older, depending on its host rock.
Uses & applications
Used for cabochons, beads, carvings, ornamental objects, and lapidary pieces; massive material has limited industrial value compared with ordinary quartz.
Geological facts
Carnelian is the red-orange variety of chalcedony, while paler yellow-orange material may be called yellow chalcedony or sard. Heating can intensify or alter its color.
Field identification & locations
Identify by its waxy appearance, translucency, hardness, and conchoidal fracture; it should resist scratching by a steel knife and not fizz in dilute acid. Common sources include India, Brazil, Uruguay, Madagascar, and the western United States.
