gemstone

Tumbled carnelian and agate

Microcrystalline quartz (chalcedony), SiO₂; iron-bearing varieties include carnelian

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; orange, red, brown, cream, and translucent banded colors; waxy to glassy luster; cryptocrystalline quartz with no visible cleavage, conchoidal fracture, and specific gravity about 2.6.

Identified September 10, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later colored red-orange by iron oxides; commonly Cenozoic to older, depending on the host rock. These pieces are human-tumbled and polished.

Uses & applications

Used for beads, cabochons, carvings, decorative stones, and inexpensive jewelry; also sold as lapidary rough and polished collectibles.

Geological facts

Carnelian is orange-red chalcedony, while agate commonly shows banding or translucent color zoning; heating can intensify its red color. Some commercial material may be dyed.

Field identification & locations

Identify by its waxy translucence, quartz-level hardness, lack of cleavage, and conchoidal fracture; glass may look similar but is generally softer and more uniform. Common sources include Brazil, Uruguay, India, Madagascar, and Indonesia.