mineral

Polished carnelian/chalcedony

Microcrystalline quartz (SiO₂), iron-oxide-colored chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to glossy luster; translucent reddish-brown body with orange-yellow zones and pale gray chalcedony. It has no visible cleavage and a cryptocrystalline quartz structure; specific gravity is about 2.58–2.64.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron oxides producing red, brown, and orange coloration. The specimen is likely naturally ancient but its smooth surface has been polished by humans.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; attractive polished pieces commonly have modest collector value.

Geological facts

Carnelian is a red-orange variety of chalcedony, while darker brown material is often called sard; boundaries between the names are gradual. Color may be enhanced by heating or dyeing.

Field identification & locations

Identify it by its waxy appearance, translucency, lack of cleavage, and inability to scratch it with a steel knife; quartz-rich chalcedony can scratch glass. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.