gemstone
Carnelian agate
Cryptocrystalline quartz (SiO₂), iron-oxide-bearing chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent orange-red to brown with glassy/waxy luster, often showing subtle banding and conchoidal fracture. It has no visible cleavage and a microcrystalline quartz structure.
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Physical properties
Hardness 6.5–7 Mohs; translucent orange-red to brown with glassy/waxy luster, often showing subtle banding and conchoidal fracture. It has no visible cleavage and a microcrystalline quartz structure.
Formation & geological history
Forms when silica-rich groundwater fills cavities in volcanic rock, with iron oxides producing the red-orange color; commonly Cenozoic to older, depending on host rock.
Uses & applications
Used for cabochons, beads, carvings, and ornamental objects; attractive specimens are popular with mineral collectors.
Geological facts
Carnelian is the red-orange variety of chalcedony; darker red material is often called sard. Heat treatment can intensify its color, so natural and treated pieces may differ in value.
Field identification & locations
Identify by its translucent warm color, waxy/glassy surface, quartz hardness, and conchoidal fracture; common sources include India, Brazil, Uruguay, Madagascar, and Germany.
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