gemstone

Banded agate/chalcedony fragment

Microcrystalline quartz (SiO₂), likely banded chalcedony or agate

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent pale tan to gray with parallel bands, vitreous to waxy luster, and no obvious cleavage. The dark markings may be iron/manganese staining or included minerals; the fragment appears cut or naturally broken.

Identified September 18, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities and fractures, depositing successive layers of chalcedony and quartz. Individual bands can form over long periods, commonly in volcanic rocks, generally from Paleozoic to Cenozoic environments.

Uses & applications

Used for cabochons, beads, carvings, polished specimens, and ornamental objects; small fragments have modest lapidary and collecting value.

Geological facts

Agate is defined by visible banding in chalcedony, while chalcedony is the broader microcrystalline-quartz category. Color and band patterns commonly result from trace iron, manganese, or other impurities.

Field identification & locations

Identify it by its waxy/glassy appearance, translucency, curved or parallel banding, and resistance to scratching with a steel blade; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.