mineral

Polished blue chalcedony (likely blue quartz/chalcedony cabochon)

Chalcedony, cryptocrystalline SiO₂; possibly dyed or treated common quartz

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; pale blue, translucent, waxy to vitreous luster, and no visible crystal faces or cleavage. The rounded cabochon is polished and may show internal fractures or treatment effects.

Identified August 17, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, precipitating as microscopic quartz fibers; deposits are commonly Cenozoic to older. Blue color can be natural from inclusions or enhanced by dye/treatment.

Uses & applications

Used for cabochons, beads, carvings, and ornamental objects; durable enough for jewelry but less valuable than fine natural blue chalcedony or blue lace agate.

Geological facts

Chalcedony is a quartz variety composed of intergrown microcrystals, so it commonly appears smooth and cloudy rather than crystalline. Strong, uniform blue color may indicate treatment.

Field identification & locations

Commonly found in volcanic regions, including Brazil, India, Turkey, Madagascar, and the United States. Identify with hardness, waxy luster, lack of cleavage, and a refractive index near 1.54–1.55; acid has no effect.