Mineral Resources Potential - Geothermal Resources

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Gemstones and Semi-precious Stones 191
pitchstone (vitric tuff) of the Algae Formation. The territory where
opal is found is quite vast, The concession areas cmot be kept
under permanent surveillance. The opal is found as spherical or
elliptical nodule with the gem opal resting inside, It is possible to
find as many as eight nodule of opal within one square meter. A
slowly cooled siliceous fluiaava upon differentiation when
extruded the thin continuous rhyolitic horizon. The gem variety
opal accounts for the formation of a densely scattered
ellipticdsphere nodules. The gem field has been estimated to
extend over an area of at least 7 x 7 km. The opal nodules average
about 10 cm in diameter. Rock with opal nodules, particularly
visible on the collapsed block, height of the level, 4m.
Recently, an opal nodule weighing 4-5 kg has been found
by local people (Fig. 41). The opal from northern Shewa shows the
internal interplay of colours, xeGealing various base colours; clear,
translucent white lavender, red or anger yellow-green and blue
- wlours (Fig. 42, '43). Such quality of precious opal is exceeded
only by the four principal and highly priced gemstones (diamond,
emerald, ruby and sapphire). Contrary to Australian opals, the red
ones are 'the most common and the blue ones the rarest. The highland
inhabitants collect the nodules, which are for sale in the
capital city later on, It is in the nature of things; but it is forbidden
to non-natives. There are seven concessions, but only three of them
are king exploited. The precious opal is currently mined by a
private company in small-scale, at Mam in northern Shew
Amham National Regional State. The precious opal mined in north
Shewa is exported largely semi-processed nodules. However, it is
recommended that precious opal be exported being cut, shaped wnd
finished here within the country. Other occurrences of precious
opal are reported in Warder, Ogaden, and Dire Dawa, and Me;
thus it is believed to be available in many parts of tbe country.