mineral

Polished carnelian/chalcedony

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, orange, and reddish zones with a waxy-to-glassy luster and no visible cleavage. It has a cryptocrystalline quartz structure and typically specific gravity near 2.6.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron oxides producing the warm coloration; deposits commonly formed in volcanic rocks during the Cenozoic or earlier. The specimen is naturally shaped and polished or highly water-worn.

Uses & applications

Used for beads, cabochons, carvings, and lapidary specimens; durable enough for ornamental objects but generally not high-value jewelry unless color and translucency are exceptional.

Geological facts

Carnelian is the orange-red variety of chalcedony, while brown material may be called sard or brown chalcedony. Color can deepen through gentle heating because iron minerals oxidize.

Field identification & locations

Identify by its waxy luster, translucency, conchoidal fracture, lack of cleavage, and inability to scratch glass only if testing is appropriate. Common sources include India, Brazil, Uruguay, Madagascar, and the western United States.