|Opal is a hydrated amorphous form of silica; its water content ranges from 3 to 21% by weight, but is usually between 6 and 10%. It is classified as a mineraloid, unlike crystalline forms of silica, which are classed as minerals.|
The first report of gem opal from Ethiopia appeared in 1994, with the discovery in the Menz Gishe District, North Shewa Province.
|The opal, found mostly in the form of nodules, is of volcanic origin and is found within weathered layers of rhyolite. In 2008, a new opal deposit was found near the town of Wegel Tena, in Ethiopia's Wollo Province.|
The Wollo Province opal was different from other Ethiopian opal finds in that it more closely resembled the sedimentary opals of Australia, with a vivid play-of-color. 'Wello' opal became the dominant Ethiopian opal in the gem trade. The finest examples are referred to as 'Imperial Opal'.
|These opals are found in a round nodular form within a 3 meter thick layer of welded volcanic ash. Only about 1% of these nodules contain colour.|
The colours are very striking with red being common and blue quite rare which is the opposite to Australian opals.
|Welo Opals are found in a plateau 2500 to 3299 meters above sea level. Only locals are allowed to mine this field. They work the horizontal level of steep mountains with basic hand tools.|
|Ethiopia Is considered one of the oldest inhabited human areas on the planet. The Awash Valley has one of the most complete preserved Australopithecine fossils, around 3.2 million years old.|