gemstone

Opal gemstone pendant

Opal (hydrated amorphous silica, SiO₂·nH₂O)

AI-generated identification · may be incorrect

The small pale, milky cabochon appears to be common white opal, with vitreous-to-waxy luster and no visible play-of-color. Hardness is approximately 5.5–6.5 Mohs; opal is amorphous, has conchoidal fracture, and specific gravity around 1.98–2.25.

Identified August 26, 2026More gemstone →

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Physical properties

Formation & geological history

Opal forms when silica-rich groundwater deposits hydrated silica in cavities, fractures, or sediments; common gem opal is especially associated with young volcanic or sedimentary terrains, often Cenozoic in age.

Uses & applications

Used for jewelry and ornamental objects; its value depends on body color, transparency, play-of-color, durability, and workmanship.

Geological facts

The image does not show enough detail to confirm natural opal versus synthetic or another white gemstone such as chalcedony, moonstone, or jade. The metal setting and chain are not geological materials.

Field identification & locations

In the field, opal is identified by low hardness, relatively low density, waxy luster, and—when precious—changing spectral flashes under movement; laboratory testing is needed for confident identification. Common sources include Australia, Ethiopia, Mexico, and Nevada, USA.