gemstone

Polished carnelian agate cabochon

Microcrystalline quartz (chalcedony), SiO₂, colored mainly by iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange-brown body with waxy to vitreous luster and no visible cleavage. The rounded, polished form is a cabochon; the pale central patch may be natural quartz/chalcedony or an inclusion.

Identified August 19, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, with iron producing orange-red coloration; subsequent burial and weathering expose it. Deposits are generally Cenozoic to older, depending on locality.

Uses & applications

Used for beads, cabochons, carvings, and decorative objects; common polished specimens typically have modest value.

Geological facts

Carnelian is an orange-red variety of chalcedony, and its color can deepen through gentle heating or prolonged sunlight exposure. It is closely related to sard, which is generally darker brown-red.

Field identification & locations

Identify it by its uniform translucent orange color, waxy surface, glass-like hardness, and lack of cleavage; it should scratch glass but not be scratched by steel easily. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.