mineral

Tumbled agate (chalcedony)

Microcrystalline quartz, SiO₂; likely translucent gray-and-white chalcedony with agate-like banding

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; gray, white, and faint brown zones with a waxy-to-vitreous luster. Quartz’s trigonal crystal structure is microscopic; it has no visible cleavage and breaks conchoidally. Specific gravity is about 2.6.

Identified October 13, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich water deposited microcrystalline quartz in cavities or fractures, commonly in volcanic rocks; agate forms over geological time, often millions of years. The stone appears naturally rounded or tumbled, with no age or locality discernible from the image.

Uses & applications

Commonly used for jewelry, beads, carvings, and decorative or collector specimens; agate is also used in precision components and abrasives.

Geological facts

Agate is a variety of chalcedony, not a separate mineral species; characteristic curved or concentric bands may be subtle or absent in small tumbled pieces.

Field identification & locations

Look for hardness, glassy/waxy luster, translucency at thin edges, and possible internal bands; common sources include Brazil, Uruguay, India, and the western United States. A small tumbled piece like this typically sells for about $1–$10 USD.