mineral

Polished agate/chalcedony fragment

Microcrystalline quartz (SiO₂), likely iron-stained chalcedony or agate

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; translucent cream, white, tan, and rusty-brown zones with a waxy to vitreous luster. Quartz has a trigonal structure and no cleavage; the irregular fracture and possible banding are consistent with chalcedony/agate.

Identified September 12, 2026More mineral →

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Physical properties

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing layered chalcedony and quartz; iron oxides create the brown-red coloration. The specimen’s exact geological age and locality cannot be determined from the image.

Uses & applications

Used for cabochons, beads, carvings, lapidary pieces, and ornamental objects; polished agate is also collected. It has little industrial value as an isolated specimen.

Geological facts

The surface appears polished or naturally smoothed, and strong lighting exaggerates its translucency and color. Agate is a variety of chalcedony distinguished by visible color banding or patterns.

Field identification & locations

Identify with glass-scratch hardness, waxy luster, translucent edges, and curved/concentric banding; avoid confusing it with colored glass or resin. Common worldwide, especially in volcanic regions of Brazil, Uruguay, Mexico, India, and the United States.