mineral

Tumbled chalcedony (likely carnelian or brown agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide coloration

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent honey-brown to orange with milky gray areas, waxy-to-glassy luster, and no visible cleavage. Its rounded shape and polished surface indicate mechanical tumbling; internal banding is subtle or absent.

Identified September 13, 2026More mineral →

Explore Tumbled chalcedony (likely carnelian or brown agate) in the encyclopedia →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later crystallizing as fibrous quartz; iron oxides create the orange-brown color. Chalcedony deposits range from ancient to modern geological ages.

Uses & applications

Used for beads, cabochons, carvings, ornamental objects, and inexpensive collector specimens; durable enough for jewelry and decorative stone.

Geological facts

Carnelian is the orange-red variety, while brown or weakly banded material is commonly sold as brown agate or chalcedony. Heating can intensify its red-orange color.

Field identification & locations

Identify by its waxy luster, translucency, quartz-like hardness, and lack of cleavage; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.