mineral

Dyed and polished agate slice

Agate, a banded microcrystalline variety of chalcedony (SiO₂), commonly quartz with minor impurities

AI-generated identification · may be incorrect

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.

Identified August 26, 2026More mineral →

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Physical properties

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.