mineral
Polished blue agate geode slice
Banded chalcedony (microcrystalline SiO₂), commonly quartz with blue dye or enhancement
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent to opaque blue-and-white concentric banding, waxy to vitreous luster, cryptocrystalline quartz, no obvious cleavage; specific gravity about 2.6. The flat polished face and cut edge indicate human processing.
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Physical properties
Hardness 6.5–7 Mohs; translucent to opaque blue-and-white concentric banding, waxy to vitreous luster, cryptocrystalline quartz, no obvious cleavage; specific gravity about 2.6. The flat polished face and cut edge indicate human processing.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and quartz in successive bands; formation commonly occurred in Cenozoic volcanic terrains, though age varies by locality. Strong electric-blue color is often artificially dyed.
Uses & applications
Used as a decorative specimen, bookend, cabochon, jewelry component, and ornamental slice; generally modest commercial value.
Geological facts
The central cavity may contain tiny quartz crystals or botryoidal chalcedony. Blue agate is frequently enhanced because naturally vivid blue material is uncommon.
Field identification & locations
Identify by concentric banding, translucent chalcedony, glassy/waxy polish, and lack of cleavage; common sources include Brazil, Uruguay, Mexico, and India. Dye may concentrate in cracks or porous zones.
