mineral

Tumbled chalcedony (likely mossy or iron-stained agate)

Microcrystalline quartz, SiO₂; chalcedony/agate variety

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent cream, olive-green, and brown coloration with a waxy to vitreous luster. It is cryptocrystalline quartz with no visible cleavage and conchoidal fracture; the rounded shape indicates tumbling and polishing.

Identified September 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, later depositing chalcedony and occasional iron-oxide inclusions. The specimen’s exact geological age and locality cannot be determined from the photograph.

Uses & applications

Used for beads, cabochons, carvings, decorative stone, and inexpensive collectible specimens; polished pieces are commonly sold as tumbled stones.

Geological facts

Iron oxides create the rusty brown zones, while microscopic mineral inclusions may produce the greenish areas. A glassy appearance, hardness, and waxy translucence help distinguish it from ordinary glass or softer jasper.

Field identification & locations

Common in volcanic terrains worldwide, including Brazil, India, Madagascar, Uruguay, and the western United States. Field tests include scratching glass, observing conchoidal fracture, and checking for a waxy texture; identification from an image is provisional.