gemstone

Tumbled carnelian/chalcedony

Carnelian, a reddish variety of microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; reddish-brown to orange, translucent in thinner areas, with a waxy to vitreous luster and no visible cleavage. The rounded shape and glossy surface suggest natural water-worn or tumbled chalcedony, possibly heat-enhanced.

Identified August 10, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, often as layered chalcedony; iron oxides create the red color. Deposits range from Paleozoic to Cenozoic in age and commonly occur in volcanic terrains and alluvial gravels.

Uses & applications

Used for beads, cabochons, carvings, seals, and ornamental objects; attractive specimens are collected as lapidary rough or polished stones.

Geological facts

Carnelian is cryptocrystalline quartz, so individual crystals are too small to see without magnification. Color may deepen with heating or dyeing, and red jasper can look similar but is generally opaque.

Field identification & locations

Check for hardness, conchoidal fracture, waxy luster, translucency, and resistance to scratching by steel; quartz-rich material should not scratch glass easily but can scratch it. Common sources include India, Brazil, Uruguay, Madagascar, Germany, and western U.S. gravels.