gemstone

Polished carnelian/chalcedony nodule

Microcrystalline quartz (SiO₂), orange-red chalcedony variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange, amber, and reddish-brown coloration with waxy to vitreous luster. It has a cryptocrystalline quartz structure, no visible cleavage, and conchoidal fracture; surface appears polished or naturally water-worn.

Identified September 13, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron oxides producing the orange-red color; commonly associated with volcanic rocks. Deposits range from ancient Paleozoic–Mesozoic formations to younger alluvial gravels.

Uses & applications

Used for cabochons, beads, carvings, ornamental objects, and polished display pieces; historically used for seals and amulets. Common material has modest value, while strongly translucent, vividly colored specimens are more desirable.

Geological facts

Carnelian is a variety of chalcedony, and color may deepen with heating or prolonged exposure to sunlight. The pale translucent patches and iron-rich orange zones are typical of banded or brecciated chalcedony.

Field identification & locations

Identify by its waxy luster, translucency, lack of cleavage, hardness, and orange-red iron staining; it should scratch glass but not be scratched by a steel knife. Common sources include India, Brazil, Uruguay, Madagascar, and the United States.