gemstone

Polished carnelian/chalcedony

Chalcedony, microcrystalline quartz (SiO₂), with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown, orange-red, cream, and gray zones; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The smooth surface indicates tumbling or polishing.

Identified September 15, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, later colored by iron oxides; commonly associated with volcanic rocks, especially Cenozoic basalts and ancient silica deposits. The specimen’s exact age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, beads, carvings, and ornamental objects; durable and affordable compared with transparent gemstones.

Geological facts

Carnelian is the orange-red variety of chalcedony, while brown or gray translucent portions may be called sard or common chalcedony. Color can be enhanced by heating.

Field identification & locations

Identify by its glassy/waxy appearance, translucency, hardness, and lack of cleavage; it should scratch glass but not be scratched by a steel blade. Common sources include Brazil, India, Uruguay, Madagascar, and the United States.