gemstone

Blue chalcedony cabochon (likely dyed)

Microcrystalline quartz, SiO₂ (chalcedony)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; deep blue, translucent to opaque, vitreous-to-waxy luster, cryptocrystalline structure, no visible cleavage, specific gravity about 2.6. The smooth domed shape and unusually uniform color suggest polishing and possible dye treatment.

Identified September 18, 2026More gemstone →

Explore Blue chalcedony cabochon (likely dyed) in the encyclopedia →

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Physical properties

Formation & geological history

Chalcedony forms when silica-rich fluids precipitate in cavities and fractures, commonly in volcanic rocks; its age varies from relatively young to ancient. Blue material occurs naturally but vivid, even blue is often enhanced by dyeing.

Uses & applications

Used for cabochon jewelry, beads, carvings, and collectors’ specimens; not generally used in construction.

Geological facts

Chalcedony is a variety of quartz composed of intergrown quartz and moganite. Blue dye may concentrate in pores, fractures, or the surface and can fade or bleed with chemicals.

Field identification & locations

Identify by its glassy/waxy polish, quartz-like hardness, lack of cleavage, and inability to scratch it with a steel knife; a loupe may reveal dye concentration. Common sources include Brazil, India, Turkey, Madagascar, and the United States.