gemstone

Tumbled carnelian/chalcedony

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent honey-brown to reddish-brown color, waxy luster, cryptocrystalline quartz structure, and no visible cleavage. The rounded surface indicates natural water wear or tumbling, with minor pits and inclusions.

Identified August 26, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich fluids fill cavities and fractures in volcanic rocks, later acquiring red-brown color from iron oxides; commonly Cenozoic to older, depending on host rock. Exact age cannot be determined visually.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive collectible specimens; durable enough for jewelry but less valuable than fine transparent gemstones.

Geological facts

Carnelian is the orange-red variety of chalcedony, while darker brown material may be called sard. Color can be enhanced by heating or dyeing, though this specimen appears naturally colored or moderately weathered.

Field identification & locations

Identify by its waxy luster, translucency, lack of cleavage, and quartz hardness; it should resist scratching from a steel file. Common sources include India, Brazil, Uruguay, Madagascar, and the western United States.