gemstone

Tumbled blue chalcedony (likely dyed)

Cryptocrystalline quartz, SiO₂; chalcedony variety

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; blue, translucent to opaque, vitreous-to-waxy luster, and no visible cleavage. The smooth rounded form is mechanically tumbled; unusually saturated blue color commonly indicates dye treatment, though blue lace agate or chrysocolla-bearing chalcedony are alternatives.

Identified August 11, 2026More gemstone →

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Physical properties

Formation & geological history

Chalcedony forms when silica-rich groundwater fills cavities and fractures, depositing microscopic quartz fibers during diagenesis or volcanic activity. Natural material is common in Cenozoic volcanic and sedimentary settings; the pictured finish is modern human processing.

Uses & applications

Used for cabochons, beads, carvings, tumbling, and inexpensive jewelry or décor. It is valued mainly for color, translucency, pattern, and polish.

Geological facts

Chalcedony is quartz composed of interlocking microcrystals, so crystal faces are usually invisible. Dye often concentrates in pores, fractures, or along edges and can fade or bleed with solvents.

Field identification & locations

Common sources include Brazil, Uruguay, Madagascar, India, Turkey, and the United States. Confirm with a loupe for dye concentration, a hardness test against glass, and avoid destructive testing; a gemological lab is needed for precise identification.