gemstone

Likely rough opal

Hydrated amorphous silica (SiO₂·nH₂O), probably common opal; the image is insufficient to confirm precious opal

AI-generated identification · may be incorrect

Small irregular yellow-brown and blue-green specimen with a dull-to-waxy luster and possible surface fractures. Opal has no crystal structure, Mohs hardness about 5.5–6.5, and no cleavage; color and play-of-color are difficult to judge from this photo.

Identified October 4, 2026More gemstone →

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Physical properties

Formation & geological history

Forms when silica-rich water deposits hydrated silica in cracks and cavities, often in volcanic rocks or sedimentary settings. Opal deposits range from geologically young to tens of millions of years old.

Uses & applications

Cut and polished opal is used in jewelry and collected; common opal is mainly ornamental. This small rough piece has limited value unless it shows attractive play-of-color when examined in person.

Geological facts

Precious opal displays shifting spectral colors from light diffraction in its internal silica spheres; common opal does not. The blue-green patches here may be color, surface reflection, or staining.

Field identification & locations

Check in daylight and from several angles for genuine moving play-of-color; opal is relatively soft and can craze if dried or heated. Opal occurs notably in Australia, Ethiopia, Mexico, and the western United States.