Ethiopian opal

Apparently from the Wollo province of Ethiopia.

Opal from Ethiopia that hit the market in 1993 from deposits near Mezezo, Shewa Province, has a tendency to craze. But the Wollo Province deposit was hailed as one of the most promising deposits of precious opal for the coming years in the Summer 2010 issue of Gems & Gemology and the Summer 2011 issue of InColor. “Wollo opal should be recognized as a new type because it can absorb or lose water, affecting transparency and play-of-color when wet, but recovering all its qualities when dry,” report researchers. They describe this new Ethiopian opal find as different from the opals of Shewa Province. Laboratory testing of the Wollo opal revealed most specimens were resistant to crazing after repeatedly being immersed in water and dried out over a period of time. Not only are they stable, researchers say, they’re surprisingly tough. 

Nine views of the specimen in this imgur album.  Video of a beautiful cab here.