Nevsun Pours First Gold at Bisha
The Bisha deposit is configured in three distinct layered zones, a 35-m-thick sur- face oxide cap having a high gold and sil- ver content immediately overlying a 30-m- thick, copper-enriched supergene zone, which itself overlies a deeper primary sul- phide zone containing both zinc and cop- per, which is open at depth. The open-pit Bisha mine will produce about 430,000 oz/y of gold from the oxide cap during its first two years of operation. During the fol- lowing three years, it will produce high- grade copper concentrate from the deposit’s supergene zone, and thereafter it will produce separate zinc and copper con- centrates from the primary zone.
Contained metal production over Bisha’s projected 10-year mine life is expected to total 1.06 million oz of gold, 9.4 million oz of silver, 734 million lb of copper, and more than 1 billion lb of zinc. Operating costs, including all royalties and credits are expected to be under $250/oz of gold, in the range of $0.54 to $0.67/lb for copper, and $0.50/lb for zinc.
The Bisha mine is based on convention- al open-pit mining methods, using heavy- duty highway trucks loaded by excava- tor/loader. The milling rate will be 5,500 mt/d of ore. The oxide ore is being processed by cyanide leaching and carbon in pulp recovery; the supergene and primary ores will be processed by flotation. Production of copper concentrate will begin at a minor amount during year two, increase to signifi- cant quantities during years three to five, and reduce to smaller quantities during years six to 10. Zinc concentrate production will occur only during years six to 10.
The state of Eritrea has a free carried 10% interest in the Bisha project, plus an additional 30% paid participating interest, for a total of 40%.