mineral

Polished banded agate (probable)

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

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; gray, brown, reddish, and cream colors with fine curved banding; waxy to vitreous luster; cryptocrystalline structure and no visible cleavage. The rounded, glossy surface indicates tumbling or polishing.

Identified September 7, 2026More mineral →

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Physical properties

Formation & geological history

Agate forms when silica-rich groundwater repeatedly fills cavities in volcanic rock, depositing chalcedony and quartz in layers; most specimens formed in ancient volcanic environments, commonly during the Paleozoic–Cenozoic. Exact age and identity require testing or a clear unpolished edge.

Uses & applications

Used for cabochons, beads, carvings, paperweights, and ornamental objects; also popular as an inexpensive collector stone. Common polished pieces generally have modest value.

Geological facts

The apparent metallic sparkle may be mica, hematite, or reflective quartz rather than true metal. Strong curved banding, translucency at thin edges, and a glass-scratching hardness test support agate identification.

Field identification & locations

Common worldwide, especially Brazil, Uruguay, Mexico, India, Madagascar, and the United States. Inspect banding with a loupe, check for translucency, and distinguish it from dyed or resin-coated material; a gemological test can confirm composition.