mineral
Dyed and polished banded agate (likely blue agate)
Microcrystalline quartz, SiO₂ (chalcedony/agate), artificially blue-dyed
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; blue and white-gray curved banding, vitreous to waxy luster, cryptocrystalline quartz, no obvious cleavage, and specific gravity near 2.6. The vivid uniform blue strongly suggests dyeing rather than a natural color.
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Physical properties
Hardness about 6.5–7 Mohs; blue and white-gray curved banding, vitreous to waxy luster, cryptocrystalline quartz, no obvious cleavage, and specific gravity near 2.6. The vivid uniform blue strongly suggests dyeing rather than a natural color.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing concentric or irregular chalcedony bands over long periods, commonly during the Cenozoic or older volcanic episodes. This piece has been cut, rounded, polished, and likely dyed by humans.
Uses & applications
Used as a decorative stone, cabochon, tumbled stone, bead, and inexpensive collector specimen; it has little architectural or industrial use beyond minor silica applications.
Geological facts
Agate’s bands record changing chemistry and flow conditions during cavity filling. Dye commonly concentrates along pores, fractures, or band boundaries and may fade or bleed with solvents.
Field identification & locations
Identify it by translucent fine banding, quartz-like hardness, and absence of cleavage; it should scratch glass but not be scratched by a steel nail. Common sources include Brazil, Uruguay, Mexico, India, and Madagascar.
