gemstone

Polished carnelian (red-orange chalcedony)

Carnelian, a cryptocrystalline variety of quartz (SiO₂)

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent reddish-orange to brown, with vitreous/waxy luster and no visible crystal faces or cleavage. Its curved, glossy surface appears polished and may show subtle color zoning.

Identified August 28, 2026More gemstone →

Explore Polished carnelian (red-orange chalcedony) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater deposits microcrystalline quartz, commonly filling cavities and veins in volcanic rocks; iron impurities create the red-orange color. Deposits occur in rocks ranging from Paleozoic to Cenozoic age.

Uses & applications

Used for cabochons, beads, carvings, seals, and ornamental objects; durable enough for jewelry and decorative stonework.

Geological facts

Carnelian is closely related to sard, which is typically darker brown-red; heating can intensify its orange-red color. It was widely used for ancient Egyptian and Roman seals.

Field identification & locations

Identify it by its orange-red translucency, waxy/vitreous polish, lack of cleavage, and hardness sufficient to scratch glass; glass imitations often contain bubbles. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.