mineral

Tumbled brown chalcedony (likely carnelian/agatesque material)

Microcrystalline quartz, SiO₂; chalcedony variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent brown to reddish-brown, waxy/glassy luster, cryptocrystalline structure, and no visible cleavage. The smooth glossy surface indicates tumbling or polishing; internal pale patches may be quartz or host material.

Identified August 28, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating as chalcedony over millions of years, commonly during the Cenozoic or older volcanic episodes. The specimen’s exact locality and age cannot be determined visually.

Uses & applications

Used for beads, cabochons, carvings, lapidary ornaments, and collections; durable pieces may be used in jewelry. Common material generally has modest commercial value.

Geological facts

Brown chalcedony may be sold as brown agate, carnelian, smoky chalcedony, or jasper depending on translucency and pattern. Color can result from iron oxides or hydroxides.

Field identification & locations

Identify by its waxy luster, translucency at thin edges, conchoidal fracture, and inability to scratch with a steel knife; it should scratch ordinary glass. Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States.