gemstone

Polished blue-gray agate

Microcrystalline quartz (chalcedony), SiO₂; likely blue lace or dyed blue agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent blue-gray body, waxy to vitreous luster, conchoidal fracture, no cleavage, and specific gravity about 2.6. The smooth shaped surface indicates a polished or cabochon-cut specimen.

Identified August 24, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony in layers over long periods, commonly during the Cenozoic or older volcanic episodes. Strong uniform blue coloration may result from dyeing, especially in commercial specimens.

Uses & applications

Used for cabochons, jewelry, carvings, ornaments, and polished collectibles; agate is also used for beads and occasional industrial precision surfaces.

Geological facts

Agate is a fibrous variety of quartz whose banding reflects changing chemistry during cavity filling. Blue lace agate is naturally pale blue with delicate white banding, while evenly saturated blue pieces are often treated.

Field identification & locations

Identify by its glassy/waxy appearance, translucency, conchoidal fracture, and inability to scratch with a steel knife; quartz should scratch ordinary glass. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and Namibia.