mineral

Tumbled purple agate (likely amethyst-bearing agate)

Banded chalcedony, a microcrystalline variety of quartz (SiO₂); exact identification is uncertain from the image

AI-generated identification · may be incorrect

Purple and white curved bands, vitreous-to-waxy luster, and polished surface; quartz hardness is about 7 Mohs, with no visible cleavage. Chalcedony has a microcrystalline structure and specific gravity near 2.6.

Identified September 26, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich fluids deposited quartz in cavities and fractures, producing layered chalcedony; age depends on the source deposit and cannot be determined from the image.

Uses & applications

Used for beads, cabochons, small ornaments, and collecting; agate is also used in some precision components.

Geological facts

Agate’s distinctive bands form as successive silica layers, sometimes colored by trace elements or inclusions.

Field identification & locations

Look for curved or concentric bands and a smooth, glassy polish; common sources include Brazil, Uruguay, India, and the United States. The pictured tumbled stone is too small for precise variety identification.