Hydrophane White Opal with Intense Fire. 570 km north of Addis Ababa, Wello (Wollo), Delanta Plateau, Tigray, Ethiopia © 2002-2010 Bonhams 1793 Ltd

Weighing approximately 10.10 carats and measuring 21.5 x 14.0 x 7.5mm - Sold for $1,464

This is an excellent precious opal from the leading local mine found in Wello province, Delanta region, around 2700 ft above sea level and 570 km northwest of the capital city Addis Ababa. Discovered in 2008 gem crystal and hydrophane opal from Wello Ethiopia has recently come to the international market. Mined only by the local farmers who are currently banding together to form small mining cooperatives, the Ethiopian Ministry of Mining and Energy is making efforts to train them on mining safety, polishing, and market conditions. Found in volcanic rock and frequently in rhyolite deposits, however, it does not form in nodules like the much more common and well-known material from the Mezezo, Shewa locality (see lot 34) and has no rocky outer matrix making it entirely different to the previously known deposit in central Ethiopia. Wello opals are described by the Gemological Institute of America as being similar in appearance to opals from Australia or Brazil.

Mineralogically speaking Wello opal is very different from Australian opal. In appearance it may be most similar to Indonesian opal (see lot 152 for an example of Indonesian opal). Australian opal is formed of silicon spheres stacked one on top of the other, creating a diffraction grating that disperses light entering the opal. The Wello material, on the other hand, has no spheres, but instead possesses a totally different structure altogether. The color display patterns range from rolling holographic orbs and dots to sheet, to flagstone to broadflash, to rolling ribbons and threads and exhibit some wave-like patterns as well.

Wello material is hydrophane opal that is porous—a Wello opal put in water may siphon up the water through capillary action, which usually causes the beautiful neon colors to disappear. Once the opal is taken out of the water and placed on something absorbent, and the water will seep out, and the colors make their appearance again as the opal dries.

This oval cabochon exhibits the most desirable qualities of this new find: some translucency, a pure white body color and lively broad flash spectral hues to the well-formed dome. The colors are vibrant and a definite 5/5 in terms of brightness.

Bonhams & Butterfields. The Nature of Opals, 10 Nov 2010. 220 San Bruno Avenue, San Francisco www.bonhams.com