mineral
Orange chalcedony (possibly carnelian)
Microcrystalline quartz, SiO₂; iron-oxide-bearing chalcedony
AI-generated identification · may be incorrectTypically Mohs hardness 6.5–7, waxy to dull luster, translucent orange-brown color, and no visible cleavage; it has a cryptocrystalline quartz structure and specific gravity near 2.60. The mottled bands and rusty inclusions suggest iron staining or brecciation.
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Physical properties
Typically Mohs hardness 6.5–7, waxy to dull luster, translucent orange-brown color, and no visible cleavage; it has a cryptocrystalline quartz structure and specific gravity near 2.60. The mottled bands and rusty inclusions suggest iron staining or brecciation.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, with iron oxides producing orange to red coloration; deposits range from volcanic-hosted cavities to sedimentary siliceous veins, commonly Cenozoic to older. The exact age and locality cannot be determined from the photograph.
Uses & applications
Used as ornamental stone, cabochons, beads, carvings, and lapidary material; small rough pieces generally have modest collecting value.
Geological facts
Carnelian is the reddish-orange variety of chalcedony, while paler orange material is often called orange chalcedony. Color may intensify with heat treatment, and iron-rich areas can weather brown or yellow.
Field identification & locations
Common sources include India, Brazil, Uruguay, Madagascar, Namibia, and the United States. Identify it by its hardness, waxy appearance, translucent edges, and lack of cleavage; it should scratch glass but not be scratched by a steel knife.
