gemstone

Polished agate or chalcedony nodule

Microcrystalline quartz (SiO₂), likely agate/chalcedony

AI-generated identification · may be incorrect

Cream, tan, and brown mottling with translucent patches and a waxy-to-glassy luster; quartz hardness is about 7 Mohs, with no cleavage and conchoidal fracture. The rounded, polished form obscures crystal structure and any natural banding.

Identified August 15, 2026More gemstone →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in layers; formation commonly occurred during the Cenozoic or older volcanic episodes. The specimen appears cut and polished, possibly tumbled.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and small collectibles; durable agate is also used for decorative stone and precision surfaces.

Geological facts

Agate’s internal patterns result from repeated changes in fluid chemistry, silica concentration, and mineral impurities during cavity filling.

Field identification & locations

Identify by testing for hardness near 7, translucent edges, waxy luster, and quartz-like conchoidal fracture; common sources include Brazil, Uruguay, Mexico, India, and the United States. The image alone cannot confirm agate versus jasper or another chalcedony variety.