gemstone

Tumbled carnelian (orange chalcedony)

Carnelian, a microcrystalline variety of quartz (SiO₂), colored mainly by iron oxides

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; orange to reddish-brown, translucent to opaque, with a waxy/glassy luster and no visible cleavage. It has a cryptocrystalline quartz structure and typically a conchoidal fracture; the smooth surface indicates tumbling and polishing.

Identified August 16, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, with iron impurities producing the orange-red color; many commercial pieces originate from Cenozoic to older volcanic terrains. Heat treatment may intensify the color.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and low-cost jewelry; historically used for seals and amulets. It is durable but less valuable than fine transparent gem material.

Geological facts

Carnelian is closely related to sard and agate, differing mainly in color and translucency. Its color can deepen when wet or under strong lighting.

Field identification & locations

Identify it by its warm orange-red color, waxy translucency, lack of cleavage, and quartz hardness; it should resist scratching by steel. Common sources include India, Brazil, Uruguay, Madagascar, and Germany.