mineral
Polished carnelian/chalcedony
Microcrystalline quartz (SiO₂), likely iron-stained chalcedony
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent honey-brown to reddish-brown, waxy to vitreous luster, cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The smooth shape indicates tumbling or polishing.
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Physical properties
Hardness 6.5–7 Mohs; translucent honey-brown to reddish-brown, waxy to vitreous luster, cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The smooth shape indicates tumbling or polishing.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures, later gaining red-brown color from iron oxides; commonly Cenozoic to older volcanic or sedimentary settings. Exact age cannot be determined from the photograph.
Uses & applications
Used for cabochons, beads, carvings, and ornamental objects; durable but generally modestly priced unless color and translucency are exceptional.
Geological facts
Carnelian is the orange-red variety of chalcedony, while brown material may be called sard or iron-stained chalcedony. Color can be naturally enhanced by heating.
Field identification & locations
Identify by its waxy luster, translucency, curved color bands or cloudy internal texture, and glass-scratching hardness; distinguish from amber, which is much softer. Common sources include India, Brazil, Uruguay, Madagascar, and Botswana.
