gemstone

Tumbled carnelian/chalcedony (likely)

Cryptocrystalline quartz, SiO₂; iron-oxide–colored chalcedony

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent orange-brown to red, with waxy/glassy luster and no visible cleavage. Microcrystalline quartz has a trigonal crystal structure, though individual crystals are not usually visible; the wet surface intensifies its color.

Identified September 1, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, later acquiring red-orange color from dispersed hematite or limonite. Most specimens are Cenozoic or older, but age cannot be determined from appearance alone.

Uses & applications

Used for beads, cabochons, carvings, ornaments, and lapidary work; attractive translucent pieces commonly have modest collector value.

Geological facts

Carnelian is the red-orange variety of chalcedony, grading into brown sard. Color may be enhanced by heating or dyeing, especially in commercial tumbled material.

Field identification & locations

Identify by its waxy luster, translucent warm color, conchoidal fracture, and ability to scratch glass; it should not fizz in dilute acid. Common sources include India, Brazil, Uruguay, Madagascar, and the United States.