mineral

Tumbled chalcedony (likely yellow/brown agate or carnelian)

Microcrystalline quartz, SiO₂; chalcedony with possible iron-oxide staining

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, honey-yellow, and brown coloration; waxy to vitreous luster; cryptocrystalline quartz with no visible cleavage and conchoidal fracture. The smooth oval shape indicates tumbling or natural water-wear.

Identified September 7, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, commonly during the Cenozoic or older volcanic episodes; iron oxides create yellow-to-brown tones. Exact age and variety cannot be determined from the photograph.

Uses & applications

Used for cabochons, beads, carvings, lapidary pieces, and decorative objects; durable enough for minor ornamental applications.

Geological facts

Agate is banded chalcedony, while carnelian is typically orange-red; this specimen appears weakly translucent and may be iron-stained chalcedony rather than a strongly banded agate.

Field identification & locations

Common in volcanic terrains and alluvial gravels worldwide, including Brazil, Uruguay, India, Madagascar, and the western United States. A glassy waxy surface, conchoidal fracture, and resistance to scratching with a steel blade support identification; quartz will not scratch glass easily but can scratch it.