mineral

Opal-bearing rock (possible common opal in host rock)

Hydrated amorphous silica, SiO₂·nH₂O, occurring in a pale host rock

AI-generated identification · may be incorrect

The specimen shows a pale blue-gray, waxy-looking patch in a tan, weathered matrix. Opal has no crystal structure, Mohs hardness about 5.5–6.5, and typically lacks cleavage; the photo does not establish its identity or full properties.

Identified October 14, 2026More mineral →

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Physical properties

Formation & geological history

Opal forms when silica-rich water deposits hydrated silica in fractures or cavities, often at low temperatures. The age and host-rock formation cannot be determined from the image.

Uses & applications

Common opal is used for ornamental carvings and jewelry; attractive pieces may be collected. The pictured specimen appears rough and of uncertain quality.

Geological facts

Precious opal displays play-of-color, while common opal does not; no clear play-of-color is visible here.

Field identification & locations

Check for a smooth, glassy-to-waxy silica patch and, if safe, test hardness and look for play-of-color under changing light. Opal occurs in volcanic rocks and sedimentary deposits in places such as Australia, Ethiopia, and the western United States.