28/04/2021
A Short History of Ethiopian Opal
Precious opal mined in Ethiopia began entering the gem and jewelry market in 1994. This opal originated from a discovery made in the Menz Gishe District in the northern part of the Shewa Province. Opal from this area occurs in a wide range of body colors. Much of the opal has a brown, red, or orange body color; however, yellow, white, and clear body colors are also found.
Shewa Province opal is found in stratified igneous rocks such as rhyolite, tuff, and ignimbrite. Although much of this opal has crazing problems, stable material enters the gem and jewelry market. These opals are often called βShewa opalsβ or βMezezo opalsβ after their locality of origin.
The most important opal discovery in Ethiopia to date was made in 2008 near the town of Wegel Tena in the Wollo Province in the northern part of the country. This opal can have vivid play-of-color flashing from a body color of clear, white, yellow, orange, or brown. It is more stable than the North Shewa opal. This material quickly became known in the trade as βwelo opal,β but the names βwolloβ and βwelloβ are also encountered.
Much of the welo opal is produced from a single area of stratified volcanic rocks. The main vein is an opalized rhyolitic ignimbrite up to one meter thick that overlies a base of clay. The opal likely formed as silica-bearing waters accumulated on top of the impermeable clay. Silica gel precipitated in the pore spaces of the ignimbrite and was later transformed into opal.