mineral

Tumbled chalcedony (likely carnelian/opaque agate)

Microcrystalline quartz, SiO₂; chalcedony with iron-oxide staining

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; waxy to dull luster, translucent gray-beige body with orange-brown zones, and no visible cleavage. It is cryptocrystalline quartz with a compact, smooth fracture and specific gravity around 2.6.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later acquiring orange coloration from iron oxides. The specimen is rounded and polished/tumbled; its precise geological age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, beads, carvings, lapidary ornaments, and decorative stone; less valuable when weakly colored or lacking banding.

Geological facts

Carnelian is orange-red chalcedony, while agate is typically banded; this piece appears more like iron-stained opaque chalcedony or a lightly patterned agate than fine gem-grade carnelian.

Field identification & locations

Commonly found in volcanic terrains, especially Brazil, India, Madagascar, Uruguay, and the western United States. Field tests include glass-scratching ability, waxy appearance, lack of cleavage, and possible conchoidal fracture; avoid confusing it with dyed quartz or glass.