Opal Nodule, from Mezzo, North Shewa Province, Ethiopia (REF:MEO0037)

Opals are formed over centuries and centuries by the action of rain removing silica particles from sandstone and carrying those particles deep underground, depositing them in fissures and cavities. As the material dries out, the microscopic silica "spheres” become packed into a tightly packed crystalline lattice forming the opals as we see them in the surrounding matrix. As light travels through this lattice formation we see the play of colours which makes opal so visually appealing.

Opals were discovered in Ethiopia in 1994 and the vast majority coming from that country are coming from mines near the town of Wengal Tena which is located in Wollo Province which mainly produce white opal. These opals were formed from the silica washed out of ancient volcanic ash.

In 2013, a further deposit was found around 30 miles northwest of the Wollo mine which produces black opals.

Often regarded as a birthstone for those born in October, Opal is also considered in some parts of the world as a traditional gift for a 14th wedding anniversary.