mineral
Dyed and polished agate slice
Agate, a banded microcrystalline variety of chalcedony (SiO₂), commonly quartz with minor impurities
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent gray, white, and vividly magenta-red bands; waxy to vitreous luster; cryptocrystalline quartz with no obvious cleavage; specific gravity about 2.60–2.65. The intense pink coloration is likely artificial dye, with a polished cut face and natural rind.
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Physical properties
Hardness 6.5–7 Mohs; translucent gray, white, and vividly magenta-red bands; waxy to vitreous luster; cryptocrystalline quartz with no obvious cleavage; specific gravity about 2.60–2.65. The intense pink coloration is likely artificial dye, with a polished cut face and natural rind.
Formation & geological history
Agate forms when silica-rich groundwater fills cavities in volcanic rocks, depositing chalcedony and quartz in successive bands, generally during volcanic activity from the Paleozoic to Cenozoic. This specimen was subsequently cut, polished, and dyed.
Uses & applications
Used as a decorative slab, paperweight, cabochon, and lapidary material; natural, high-quality agate is used in jewelry and ornaments. Dyed slices are typically inexpensive décor or craft specimens.
Geological facts
Concentric banding records changing chemistry and fluid conditions during cavity filling. Dye often concentrates in porous zones and fractures, producing colors rarely this saturated in natural agate.
Field identification & locations
Identify by curved banding, quartz-like hardness, waxy translucency, and a contrasting rough rind; a steel knife should not scratch it. Common sources include Brazil, Uruguay, Mexico, India, and Madagascar.
