mineral

Tumbled blue-gray chalcedony (likely blue agate)

Chalcedony, microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; blue-gray, opaque to slightly translucent, with a waxy to glassy luster and no visible cleavage. The smooth rounded shape indicates mechanical tumbling and polishing.

Identified August 11, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; blue-gray, opaque to slightly translucent, with a waxy to glassy luster and no visible cleavage. The smooth rounded shape indicates mechanical tumbling and polishing.

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing microscopic quartz fibers; it is commonly associated with volcanic rocks and formed over geologic timescales. Exact age and locality cannot be determined from the photograph.

Uses & applications

Used as a lapidary stone for tumbled specimens, cabochons, beads, carvings, and decorative objects; it is less commonly used industrially than ordinary quartz.

Geological facts

Blue coloration may result from finely dispersed minerals or inclusions; many commercially sold blue chalcedonies are naturally gray-blue, while strongly vivid blue pieces may be dyed.

Field identification & locations

Identify by its even fine-grained texture, waxy luster, lack of cleavage, and ability to scratch glass; quartz crystal points and banding may be absent. Common sources include Brazil, Uruguay, India, Madagascar, Namibia, and the United States.