mineral

Tumbled agate (likely chalcedony)

Microcrystalline quartz, SiO₂; agate is banded chalcedony, though banding is not clear in this specimen

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; brown, cream, and translucent white, with a waxy to glassy luster and no visible cleavage. Quartz has a trigonal crystal structure; this small rounded specimen appears naturally or mechanically smoothed.

Identified September 29, 2026More mineral →

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Physical properties

Formation & geological history

Silica-rich groundwater deposits chalcedony in cavities and fractures, commonly in volcanic rocks; the specimen’s age and source cannot be determined from the image.

Uses & applications

Used for jewelry, beads, ornaments, and lapidary collecting; agate is also used for decorative objects and, historically, precision instrument parts.

Geological facts

Agate’s characteristic bands form through repeated silica deposition, but not all chalcedony is visibly banded.

Field identification & locations

Look for waxy translucence, hardness near 7, and any fine curved bands when viewed under strong light; common sources include Brazil, Uruguay, India, and the United States. The image shows a small polished-looking specimen, but its exact identity is uncertain.