mineral

Polished banded agate (likely gray-and-white chalcedony)

Banded chalcedony, microcrystalline SiO₂

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pale gray, white, and tan bands with a waxy to vitreous luster. Trigonal quartz in microscopic fibers; no prominent cleavage, with conchoidal fracture. The specimen is polished and shaped.

Identified September 25, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich fluids deposited successive layers in a cavity or fracture, later hardening into banded chalcedony. Agates formed in many geological periods, commonly in volcanic rocks; the image does not establish a specific age or locality.

Uses & applications

Used for jewelry, carvings, ornaments, and lapidary practice; agate is also used for small precision components.

Geological facts

Agate banding records changing conditions during silica deposition; the pictured piece appears to be a small polished freeform or cabochon-like cut.

Field identification & locations

Look for curved or parallel color bands and a smooth, waxy surface; verify hardness or translucency only on an inconspicuous area. Agates occur worldwide, notably in Brazil, Uruguay, India, and the western United States.