gemstone

Polished precious opal cabochon

Opal (hydrated amorphous silica, SiO₂·nH₂O)

AI-generated identification · may be incorrect

Shows vivid red, orange, green, and blue play-of-color in a dark body; vitreous to waxy luster, no cleavage, hardness about 5.5–6.5 Mohs. Opal is amorphous, not crystalline; exact variety and treatment cannot be confirmed from the image.

Identified October 11, 2026More gemstone →

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Physical properties

Formation & geological history

Silica-rich water deposited microscopic silica spheres in rock cavities and fissures, where they gradually formed opal; deposits range from geologically recent to tens of millions of years old. The dark base may be natural or treated.

Uses & applications

Cut and polished as jewelry, especially cabochons; also collected as a gemstone.

Geological facts

Its shifting colors arise from diffraction by regularly arranged microscopic silica spheres.

Field identification & locations

Look for changing spectral flashes as the stone or light moves; common sources include Australia, Ethiopia, and Mexico. Avoid heat and sudden drying, which can cause cracking.