mineral

Blue chalcedony (likely common blue agate)

Microcrystalline quartz, SiO₂; chalcedony variety

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent pale blue to blue-gray, waxy to vitreous luster, cryptocrystalline structure, no cleavage, conchoidal fracture, specific gravity about 2.60. The smooth rounded form appears tumbled and polished.

Identified August 11, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks; coloration may result from trace minerals or microscopic inclusions. Individual deposits range from Cenozoic to older volcanic ages.

Uses & applications

Used for cabochons, beads, carvings, and ornamental objects; durable enough for jewelry and decorative stonework. Common polished pieces generally have modest value.

Geological facts

Blue chalcedony is often confused with dyed agate, blue opal, or glass; uniform intense color can indicate treatment. It may show subtle cloudy translucence rather than banding.

Field identification & locations

Commonly found in volcanic regions of Brazil, Uruguay, Madagascar, Turkey, Namibia, and the United States. Identify it by its cool waxy appearance, translucence, quartz hardness, and lack of bubbles or flow lines; definitive identification may require testing.