First printed in ‘Gems and Jewellery’
Ethiopia is a rising star on the African continent as a source of coloured gems.
The list of gemstones discovered to date in Ethiopia is certainly impressive:
Opal, Garnet (Almandine and Grossular), Peridot, Tourmaline, Moonstone, Sunstone, Sapphire, Ruby, Amethyst, Smokey Quartz, Citrine, Tektite, Topaz, Epidote, Sinhalite, Emerald, Aquamarine, Golden Beryl and Zircon.
The mining of opal, emerald, sapphire and amethyst has become an important source of income for people in the remote areas of the country and the government has made the utilization of their mineral wealth one of the countries principal objectives.
From left to right: Figure 1, Figure 2, Figure 3
In 1964, the discovery of gem opal in the northern region of Shewa Province was significant enough for Ethiopia to achieve recognition as an important opal producing nation. With subsequent discoveries Ethiopia has begun to rival Australia as a major source of fine opals.
The typical spheres recovered from the Shewa deposit occurred in an igneous matrix. They ranged in size from that of a golf ball to a cricket ball and most of them carried the familiar three-legged Mercedes emblem see fig 1. When broken open they generally revealed a magnificent play of fire against a chocolate, or more rarely red body colour figs 2 & 3.
Regrettably much of this opal is prone to crazing. The honeycomb pattern evident in fig 2 is encountered in both Shewa and Welo opals, see fig 4.
Figure 4: Honeycomb pattern in Shewa rough.
The Welo opal deposit was discovered in 2008 near the village of Wegel Tena in the Wollo Province some 550 klms to the north-east of Addis-Ababa.
The Welo opal is mostly white to somewhat translucent and milky however some of the material is transparent and colourless, fire opal type or brownish. The opaque to translucent material becomes transparent when it is immersed in water (hydophane).
In 2013 another opal deposit was discovered further to the north in Wollo Province. With a translucent grey to black body colour this material exhibits a good play of colour. Personal experience revealed that the play of colour can be localised within large areas of common opal. It was also disappointing that most of the cabochons I cut from this material crazed and cracked.
A recent discovery that is yielding some fine emeralds is located near the village of Dermi in the Seba Boru District. The nearest town is Shakiso, about 160 Klms north of the established emerald mine at Dubuluk close to the border with Kenya. The mining is still done traditionally but despite this there is still a good production of rough. The material is similar to Zambian emerald in character. Most of the production is commercial grade although fine stones have been cut that did not require oiling. The crystals are generally associated with dark brown to black biotite mica, quartz and kaolinite. This emerald has the same physical properties as Zambian stones. Typical inclusions are platelets of biotite, growth tubes and multi-phase cavities.
A new source of sapphire has been discovered in the Tigray region of Ethiopia where the artisanal miners are recovering rounded crystals from secondary alluvial deposits. Much of the material is distinctly pleochroic carrying an intense dark blue hue with quite marked green dichroism.
The typical inclusions are twinning planes, fingerprints, crystallites, tubules and rutile needles. The majority of the production is dark and would benefit from heat treatment to lighten the colour but a small percentage of the rough is suitable for faceting without any treatment.
Ethiopia is a vast country with a complex geology, this can be seen by the variety of minerals that have already been
discovered there. In today’s world it sometimes feels like there is nothing new to be found. Ethiopia is reminding us that there is always something new coming out of Africa. I wonder what other hidden treasures are waiting to be discovered.