mineraloid

Ethiopian Opal (Welo Opal)

Hydrated Amorphous Silica (SiO2·nH2O)

Hardness: 5.5-6.5 (Mohs scale); Color: White/yellow base with vivid play-of-color; Luster: Vitreous to waxy; Crystal structure: Amorphous (non-crystalline); Cleavage: None (conchoidal fracture); Specific gravity: 1.9-2.2.

Hardness: 5
Color: White/yellow base with vivid play-of-color
Luster: Vitreous to waxy

Identified March 25, 2026More mineraloid →

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Physical properties

Formation & geological history

Formed from silica-rich volcanic fluids filling cavities in volcanic rocks (rhyolite). Most Ethiopian opals date to the Miocene epoch (approx. 15-20 million years ago) and are found in the Wollo Province.

Uses & applications

Primarily used in fine jewelry (rings, pendants, earrings) and as a highly desirable specimen for gemstone collectors due to its intense 'fire' or play-of-color.

Geological facts

Ethiopian opals are often 'hydrophane,' meaning they can absorb water and temporarily lose their color or become transparent, regaining it once they dry out. The Welo deposit was only discovered in 2008.

Field identification & locations

Identify in the field by its distinct rainbow 'play-of-color' within a translucent body; it is lighter than quartz. Common locations include the Ethiopian Highlands, Australia, and Mexico. Collectors should look for body tone and color intensity.

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