Siguiri Gold Mine, Guinea
The Siguiri gold mine is found within the Siguiri District in the north-east of the Republic of Guinea, West Africa, about 850km from the capital city of Conakry. The nearest important town is Siguiri (approximately 50,000 inhabitants), located on the banks of the Niger River. Bamako, the capital of Mali is 300km away.
A majority stake in the mine (85%) was bought by Ashanti Goldfields in 1996 and became a part of AngloGold Ashanti when the two companies merged in 2004. The government of The Republic of Guinea holds a 15% interest in the mine. The first shipment of gold from Siguiri took place in April 1998 with production expected to continue until 2018.
Total production for 2009 was 316,000oz compared with the 333,000oz the previous year.
Around 2,973 employees and contractors work at the Siguiri mine. Total capital expenditure on the project for 2007 was $US22m.
The mine is located in the heart of an ancient gold mining region, thought to have been known since the 13th century as the basis of the Mandingo Empire. At its peak this empire controlled an area in West Africa the size of the United States.
Unlike in many other areas in Africa, the orpaillage (translated as gold-washing), or artisanal mining system is highly formalised and forms an integral part of village structures.
However, there have been numerous clashes between the miner AngloGold Ashanti and some groups of artisanal miners who have been found operating beyond the traditional orpaillage system and therefore agreed areas. On some occasions, mainly during the rainy season, as many as 10,000 people have been involved in pit invasions when artisanal workings are flooded or inaccessible. AngloGold recently announced that it had engaged the services of a specialist consultancy to assist with future disputes.
Leading gold producer Barrick Gold had a royalty entitlement of 1.875% on the Siguiri mine, capped on a dollar basis and with $US 15m still being paid. This entitlement was sold in June 2008 to precious metals Royalty company Royal Gold as part of a portfolio of Barrick assets valued at $US 150m.
Geology and reserves
This concession is dominated by Proterozoic Birmian rocks which consist of turbidite facies sedimentary sequences. There are essentially two kinds of gold deposit that occur in the Siguiri basin: laterite or CAP mineralisation and in situ quartz vein-related mineralisation. The first appears as aprons of colluvial or as palaeo-channels of alluvial lateritic gravel adjacent to, and directly above, the latter.
The quartz vein-related mineralisation is hosted in meta-sediments with the better mineralisation associated with vein stockworks that occurs preferentially in the coarser, brittle siltstones and sandstones. The mineralised rocks have been deeply weathered to below 100m in places to form saprolite or SAP mineralisation.
AngloGold Ashanti had Mineral Resources of 67.49Moz and Ore Reserves of 21.62Moz at 31 December 2009 in continental African region. Of these, Siguiri accounted for Ore Reserves of 3.25Moz and Mineral Resources of 5.94Moz.
Mining and processing
The ore and waste is mined by a mining contractor in a conventional open-pit mining operation. Ore is treated using carbon-in-pulp (CIP) and heap-leach processes. In 2009, the CIP plant increased volumes to 10.4Mt.
Better than expected production was achieved at Siguiri during 2007. Total production was up nine percent to 280,000 ounces compared with 256,000 ounces the previous year.
The Boure area, where Siguiri’s current mining activity is focused, is home to around 40,000 people in 12 villages – Kintinian, Boukaria, Balato, Fatoya, Kofilani, Samany, Kourouni, Kamatiguiya, Setiguiya, Kourouda, Lenkekoe and Fenserekolen – all within the sub-prefecture of Kintinian.
Further exploration here and at nearby Sintroco saw a further 1.3Moz converted to reserves. The design of a second gravity concentrator and de-gritting facilities was finalised and installed during 2009, with improved productivity expected. Studies to increase throughput are under way since 2010.
Attributable gold production in 2009 fell by 5% to 316,000oz. Mining of lower grade zones mine after the high grade pits were depleted led to the decline. Production was also impacted due to loss of days of operation after the government of Guinea ordered several stoppages.
The current estimated liabilities at Siguiri are $35.7m – $17.9m for rehabilitation and $17.8m for decommissioning. These will be provided for by the company over the life of mine.
The Mandingo Empire
Peaking some time during the 13th century, the Mandingo Empire once controlled an area in West Africa the size of the United States, a feat it was able to achieve largely because of its vast gold reserves.
With a rich cultural history that has its origins in the ancient Mali Empire, the Mandingo population numbers around 5.3 million people spread across some ten West African countries. Between 800 and 1400 AD, many of the Mandingo people converted to Islam. This trend, combined with a series of Islamic holy wars that occurred between 1855 and 1890, has resulted in over 99% of the Mandingo people currently practising Islam.