gemstone

Tumbled carnelian (likely reddish chalcedony)

Chalcedony, microcrystalline quartz (SiO₂), iron-oxide colored

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; orange-red to salmon with cloudy, mottled translucency; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage, conchoidal fracture, and specific gravity about 2.6. The smooth rounded shape indicates tumbling and polishing.

Identified August 19, 2026More gemstone →

Explore Tumbled carnelian (likely reddish chalcedony) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, later becoming microcrystalline quartz; iron impurities produce the red-orange color. Deposits occur in volcanic and sedimentary rocks, generally ranging from Paleozoic to Cenozoic age.

Uses & applications

Used for beads, cabochons, carvings, ornamental objects, and inexpensive jewelry; historically valued as a seal-stone and amulet.

Geological facts

Carnelian is a red-orange variety of chalcedony, grading toward brown sard or yellow-orange chalcedony. Heating can intensify its color by oxidizing iron.

Field identification & locations

Identify by its orange-red color, waxy appearance, translucency at thin edges, and lack of cleavage; it should scratch glass but not quartz. Common sources include India, Brazil, Uruguay, Madagascar, and the United States.