gemstone

Dyed blue agate slice

Agate, a banded variety of microcrystalline quartz (SiO₂)

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; blue color is likely dye-enhanced, with a waxy to vitreous luster and cryptocrystalline structure. It appears polished and rounded, with faint internal banding or translucency.

Identified August 17, 2026More gemstone →

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Physical properties

Hardness 6.5–7 Mohs; blue color is likely dye-enhanced, with a waxy to vitreous luster and cryptocrystalline structure. It appears polished and rounded, with faint internal banding or translucency.

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony in successive layers over millions of years. Common source regions include Brazil, Uruguay, Mexico, India, and Madagascar.

Uses & applications

Used for cabochons, ornaments, worry stones, bookends, and inexpensive jewelry; polished specimens are popular with collectors.

Geological facts

Bright, uniform blue is uncommon naturally and usually indicates dye treatment, often applied to porous gray or pale agate. Agate is chemically stable but can fade with prolonged sunlight or harsh chemicals.

Field identification & locations

Identify it by its very high polish, translucency at thin edges, curved or concentric banding, and quartz-like hardness; it should scratch glass but not be scratched by a steel knife. Look for dye concentration in cracks and along the edges.