mineral

Tumbled banded agate (likely chalcedony)

Banded microcrystalline quartz, SiO₂; chalcedony variety

AI-generated identification · may be incorrect

Opaque to translucent gray-blue with pale horizontal bands and a waxy-to-glassy luster; quartz has Mohs hardness 7 and trigonal crystal structure, though crystals are microscopic. The rounded shape and smooth surface suggest tumbling; identification from the photo is not definitive.

Identified October 5, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich fluids deposited successive layers in a cavity or fracture, later solidifying as chalcedony; the specimen’s geological age and source cannot be determined visually.

Uses & applications

Often used for lapidary, jewelry, ornaments, and collecting; agate is also used for small decorative objects.

Geological facts

Agate banding records successive mineral deposition, and its colors can vary widely depending on trace impurities.

Field identification & locations

Look for curved or parallel bands and a very hard, compact texture; agate occurs worldwide in volcanic rocks and cavities. Approximate value: $2–$20 for a small common tumbled piece.