mineral

Tumbled blue chalcedony, likely blue agate

Chalcedony (microcrystalline quartz, SiO₂), possibly dyed

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent sky-blue body with cloudy white patches, vitreous to waxy luster, cryptocrystalline structure, and no visible cleavage. The smooth rounded shape indicates tumbling; unusually vivid blue may indicate dye treatment.

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Chalcedony forms when silica-rich groundwater fills cavities and fractures in volcanic rock, commonly during the Cenozoic and older volcanic episodes. Blue agate varieties occur worldwide, notably in Brazil, Uruguay, Namibia, Turkey, and the western United States.

Uses & applications

Used for inexpensive cabochons, beads, ornaments, and lapidary pieces; common tumbled specimens usually have modest value.

Geological facts

Natural blue chalcedony is generally pale and softly colored; intense electric blue commonly signals dyeing. It is chemically the same silica mineral family as agate, jasper, and ordinary quartz.

Field identification & locations

Check for curved or banded internal patterns, glassy-to-waxy luster, and hardness sufficient to scratch ordinary glass; concentrated color in cracks or surface pits suggests dye. A gemological test or specific-gravity measurement is needed for certainty.