mineral

Blue agate (likely dyed and polished)

Microcrystalline quartz, SiO₂ (chalcedony); blue color may be dye

AI-generated identification · may be incorrect

Polished, opaque-to-translucent blue pebble with a glossy luster. Quartz hardness is 6.5–7 Mohs; trigonal crystals form a microcrystalline aggregate, typically with no visible cleavage. The image does not show diagnostic banding, so identification is provisional.

Identified September 29, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms as silica-rich fluids fill cavities in volcanic rock and deposit chalcedony in layers; deposits range from ancient to geologically recent. Bright, uniform blue in polished pieces commonly results from dyeing.

Uses & applications

Used for beads, cabochons, ornaments, and collectibles; agate is also used in precision components and decorative objects.

Geological facts

Agate is a variety of chalcedony, itself a microcrystalline form of quartz. Dyeing can intensify colors that are uncommon in natural agate.

Field identification & locations

Check for fine, curved bands and natural color variation; unusually uniform vivid blue may indicate dye. Common sources include Brazil, Uruguay, India, and the United States.