gemstone

Polished banded agate (likely chalcedony)

Microcrystalline quartz/chalcedony, SiO₂, with possible iron-oxide inclusions

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; translucent gray, lavender, cream, and yellow-brown bands with a waxy to vitreous luster. It has cryptocrystalline quartz structure, no obvious cleavage, and typically specific gravity near 2.6.

Identified August 9, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing successive layers over time; the specimen appears tumbled or polished. The host volcanic rocks may range from Paleozoic to Cenozoic in age depending on locality.

Uses & applications

Used for cabochons, beads, carvings, bookends, and decorative objects; its durability makes it popular in jewelry and lapidary work.

Geological facts

Color zoning commonly reflects trace iron and other impurities, while the curved outer outline is typical of cavity-filled agate nodules.

Field identification & locations

Identify it by its fine banding, waxy appearance, hardness, and lack of visible granular crystals; common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the United States.