St Barbara Limited, an Australian-based company, operate an open pit gold (and silver) mine called the Simberi Oxide Gold Project in the volcanic highlands on the eastern side of the island.[1] The mine is wholly owned and operated by St Barbara Limited, who acquired the assets of Allied Gold, the previous operators of the Simberi mine, on 31 August 2012.[1] Gold production started in February 2008.[1] Mining was suspended in December 2009 after Allied Gold received a cease work order from the Mineral Resources Authority of Papua New Guinea because of local landholder issues.[1] Mining has since recommenced.[1]
Seven gold deposits have been defined in mining lease 136 (ML 136), which covers the central and eastern portion of Simberi Island, and other prospects have been identified.[1][6] The gold deposits occur mainly on ridge tops and are all within 2–3 km (1–2 mi) of each other.[1][6] Sorowar in the north is the largest resource while Samat North, South and East to the south are relatively small but relatively high grade.[6] Pigiput, Pigibo and Botlu South lie between the Sorowar and Samat areas and are of intermediate tonnage but at a grade similar to Sorowar.[6] The western area of Simberi Island within exploration license EL 609 is largely unexplored.[7] Reconnaissance exploration for both oxide and sulphide mineralisation is planned.[7]
As of June 2009, Allied reported that the total resources were 4.7 million troy ounces (5.2 million ounces; 150 million grams) (Moz) gold, being oxide gold resources of 1.4 million ozt (1.5 million oz; 44 million g) and sulphide gold resources of 4.7 million ozt (5.2 million oz; 150 million g) together with 10.2 million ozt (11.2 million oz; 320 million g) silver.[6]
Ore is delivered to the processing facilities on the eastern coast near Pigiput Bay by a 2,665 m-long (8,743 ft) RopeCon aerial conveyor that can deliver 600 tonnes (590 long tons; 660 short tons) of ore per hour.[1][8] The process plant is a conventional carbon-in-leach (CIL) gold process plant capable of treating 2.2 million tonnes (2.2 million long tons; 2.4 million short tons) of ore per year.[6] In September 2010, Allied announced that it planned to increase its gold production to 100,000 troy ounces (110,000 oz; 3,100,000 g) per year.[7] The oxide processing circuit at the Simberi operation will be expanded to 3.5 million tonnes (3.4 million long tons; 3.9 million short tons) a year, by June 2013.[9]
Mine tailings are disposed of in the form of a slurry that has been pre-diluted with seawater using a deep sea tailings pipeline.[1] The pipeline is 528 m (1,732 ft) long with the discharge point at a depth of 130 m (430 ft). The tailings flow down a steep submarine slope and are deposited at a depth of more than 3 kilometers (1.9 mi).[6]
Production for the period from 1 July 2009 to 30 June 2010 was 64,327 troy ounces (70,576 oz; 2,000,800 g).[10]
In June 2009, Allied reported that the remaining mine life was estimated to be over 10 years.[6] St Barbara Limited (Australia) acquired Allied in September 2012 and is the current owner of this mining operation.[11] They are the largest employer on the island.[6]
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