A chemical slurry, with sub-microscopic gold on the surface of the bubbles, flows through a tank at Mill 5 at Newmont Mining's Carlin gold mine operation near Elko, Nevada May 22, 2014. The mill processes approximately 15,000 tons of ore a day. REUTERS/Rick Wilking (UNITED STATES - Tags: BUSINESS COMMODITIES)

A prospector sorts gold particles found at the Marco gold mine in Mukungwe locality in Walungu territory of South Kivu May 10, 2014. Decades of corruption, mismanagement and violence have blighted the development of Congo, which at the time of independence in 1960 was Africa's second most industrialised economy. In 2013 it was near the foot of global tables for per capita economic output. Now industrial mining operations are moving back to regions that have been the preserve of artisanal miners since the collapse of Congo's state-run mining operations in the 1990s, at the end of dictator Mobutu Sese Seko's 31-year rule. Picture taken May 10, 2014. REUTERS/Kenny Katombe (DEMOCRATIC REPUBLIC OF CONGO - Tags: BUSINESS EMPLOYMENT INDUSTRIAL COMMODITIES POLITICS CIVIL UNREST)

A former Seleka soldier looks at a woman washing extracted soil and small rocks as she pans for gold near an open-pit at the Ndassima gold mine near Djoubissi, north of Bambari May 9, 2014. REUTERS/Siegfried Modola (CENTRAL AFRICAN REPUBLIC - Tags: BUSINESS COMMODITIES SOCIETY MILITARY TPX IMAGES OF THE DAY)

Prospectors work at an open-pit at the Ndassima gold mine, near Djoubissi north of Bambari May 9, 2014. REUTERS/Siegfried Modola (CENTRAL AFRICAN REPUBLIC - Tags: BUSINESS COMMODITIES SOCIETY TPX IMAGES OF THE DAY)

The KCD open pit gold mine at the Kibali mining site in northeast Democratic Republic of Congo, May 1, 2014. The $2.5 billion gold mine, a joint venture between Randgold, AngloGold Ashanti and Congo's state gold miner Sokimo, poured its first gold in September 2013 and has the potential to become one of the biggest in the world, transforming the economy of this forgotten corner of one of the world's poorest and most conflict ridden countries. Picture taken May 1, 2014. REUTERS/Pete Jones (DEMOCRATIC REPUBLIC OF CONGO - Tags: BUSINESS COMMODITIES)

A prospector pans for gold in a hole in a cocoa farm that is turning into a gold mine near the town of Bouafle in western Ivory Coast March 18, 2014. With high prices for the precious metal fuelling a gold rush in Ivory Coast and Ghana, diggers are scurrying to cash in. But the drain on the labour market and the harm done to cocoa plantations could endanger cocoa production in the two nations, which account for 60 percent of global supply. Picture taken March 18, 2014. To match Insight COCOA-GOLD/WESTAFRICA REUTERS/Luc Gnago (IVORY COAST - Tags: AGRICULTURE BUSINESS COMMODITIES EMPLOYMENT)

Prospectors pan for gold at a new gold mine found in a cocoa farm near the town of Bouafle in western Ivory Coast March 18, 2014. With high prices for the precious metal fuelling a gold rush in Ivory Coast and Ghana, diggers are scurrying to cash in. But the drain on the labour market and the harm done to cocoa plantations could endanger cocoa production in the two nations, which account for 60 percent of global supply. Picture taken March 18, 2014. To match Insight COCOA-GOLD/WESTAFRICA REUTERS/Luc Gnago (IVORY COAST - Tags: AGRICULTURE BUSINESS COMMODITIES EMPLOYMENT TPX IMAGES OF THE DAY)

Prospectors pan for gold and diamonds near the town of Gaga April 6, 2014. REUTERS/Goran Tomasevic (CENTRAL AFRICAN REPUBLIC - Tags: BUSINESS COMMODITIES SOCIETY TPX IMAGES OF THE DAY)

The Tamgak open air uranium mine is seen at Areva's Somair uranium mining facility in Arlit, September 25, 2013. Picture taken September 25, 2013. To match Special Report NIGER-AREVA/ REUTERS/Joe Penney (NIGER - Tags: BUSINESS COMMODITIES ENERGY ENVIRONMENT)

A general view of makeshift shelters erected by some estimated 2000 miners who camped at an open-pit gold mine is seen in Lukingi village in Mubende district, about 150 km (90 miles) southwest of Uganda's capital Kampala November 17, 2013. Picture taken November 17, 2013. REUTERS/James Akena (UGANDA - Tags: BUSINESS COMMODITIES ENVIRONMENT SOCIETY)

A boy washes stone dust in search of gold nuggets at an open-pit gold mine in Lukingi village in Mubende district, about 150 km (90 miles) southwest of Uganda's capital Kampala November 17, 2013. Picture taken November 17, 2013. REUTERS/James Akena (UGANDA - Tags: BUSINESS COMMODITIES ENVIRONMENT SOCIETY)

A gold mine worker displays gold in a local mine in Al-Ibedia locality at River Nile State, July 30, 2013. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: SOCIETY BUSINESS COMMODITIES EMPLOYMENT)

Crushed rock samples, that is thought to contain gold, is washed at a mine in Minna, Niger State June 23, 2013. Picture taken June 23, 2013. REUTERS/Afolabi Sotunde (NIGERIA - Tags: ENERGY BUSINESS SOCIETY EMPLOYMENT)

A worker pans gold at the Wad Bushara gold mine near Abu Delelq in Gadarif State, Wad Bushara April 27, 2013. Sudan exported $2.2 billion worth of gold last year and hopes to produce around 50 tonnes of gold in 2013, which would potentially make it Africa's third-largest gold miner and push it into the top 15 producers globally. The Wad Bushara gold mine has about 2,000 workers who earn an average of $15 a day. Picture taken April 27. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS COMMODITIES EMPLOYMENT TPX IMAGES OF THE DAY)

A worker shows gold found through gold panning at the Wad Bushara gold mine near Abu Delelq in Gadarif State, Wad Bushara April 27, 2013. Sudan exported $2.2 billion worth of gold last year and hopes to produce around 50 tonnes of gold in 2013, which would potentially make it Africa's third-largest gold miner and push it into the top 15 producers globally. The Wad Bushara gold mine has about 2,000 workers who earn an average of $15 a day. Picture taken April 27. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS EMPLOYMENT COMMODITIES)

Workers pan for gold at the Wad Bushara gold mine near Abu Delelq in Gadarif State, Wad Bushara April 27, 2013. Sudan exported $2.2 billion worth of gold last year and hopes to produce around 50 tonnes of gold in 2013, which would potentially make it Africa's third-largest gold miner and push it into the top 15 producers globally. The Wad Bushara gold mine has about 2,000 workers who earn an average of $15 a day. Picture taken April 27. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS EMPLOYMENT COMMODITIES)

A worker pans for gold at the Wad Bushara gold mine near Abu Delelq in Gadarif State, Wad Bushara April 27, 2013. Sudan exported $2.2 billion worth of gold last year and hopes to produce around 50 tonnes of gold in 2013, which would potentially make it Africa's third-largest gold miner and push it into the top 15 producers globally. The Wad Bushara gold mine has about 2,000 workers who earn an average of $15 a day. Picture taken April 27. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS EMPLOYMENT COMMODITIES)

Toposa girls pan for gold in the Singaita River in Namorinyang, South Sudan October 24, 2012. In South Sudan ordinary people have been extracting gold from artisanal mines and taking part in as-yet unregulated trade in the precious metal. But now the government hopes to pass mining legislation that will formalise the industry, let them tax precious metal and mineral exports and sell concessions to large-scale investors. Officials say firms from China, Australia, the United States, South Africa and other African countries plan to apply for licences when new mining laws are passed in November. After many delays, parliament is set to begin debate on the bill on Monday. Picture taken October 24, 2012. REUTERS/Adriane Ohanesian (SOUTH SUDAN - Tags: BUSINESS COMMODITIES POLITICS CRIME LAW) ATTENTION EDITORS: PICTURE 05 OF 25 FOR PACKAGE 'SOUTH SUDAN STRIKES GOLD'. SEARCH 'SUDAN GOLD' FOR ALL IMAGES

Artisanal gold miner Mamadou Diarra poses for a picture in between panning for gold at a small scale mine in Kalana August 26, 2012. Gold mining in Mali has rebounded since the landlocked West African nation's coup d'etat in late March and 2012 national gold production estimates stand at 500 tonnes. REUTERS/Joe Penney (MALI - Tags: BUSINESS COMMODITIES EMPLOYMENT SOCIETY)

Artisanal gold miner Sara Moulare (C), 29, and colleagues pan for gold in Kalana August 26, 2012. Gold mining in Mali has rebounded since the landlocked West African nation's coup d'etat in late March and 2012 national gold production estimates stand at 500 tonnes. REUTERS/Joe Penney (MALI - Tags: BUSINESS EMPLOYMENT COMMODITIES)

Artisanal gold miner Mamadou Diarra pans for gold at a small scale mine in Kalana August 26, 2012. Gold mining in Mali has rebounded since the landlocked West African nation's coup d'etat in late March and 2012 national gold production estimates stand at 500 tonnes. REUTERS/Joe Penney (MALI - Tags: BUSINESS SOCIETY COMMODITIES)

Boys pan for gold on a riverside at Iga Barriere, 25 km (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo February 16, 2009. Ituri is one of many areas of the country to have experienced bitter ethnic conflict between rival tribes in recent years. Massacres have left tens of thousands dead. It is this fighting that led U.S. authorities to take the unprecedented step of naming Congo in section 1502 of the Dodd-Frank financial regulation act, which says U.S.-listed companies that source gold, tungsten, tantalum and tin from Congo or its neighbours must assure the U.S. stock exchange regulator that their business is not helping fund conflict. Picture taken February 16, 2009. To match Feature GOLD-CONFLICT/ REUTERS/Finbarr O'Reilly/Files (DEMOCRATIC REPUBLIC OF CONGO - Tags: ENERGY ENVIRONMENT BUSINESS EMPLOYMENT CONFLICT SOCIETY)

An artisanal miner pans for diamonds, which fuelled the 1991-2002 civil war, in the town of Koidu in eastern Sierra Leone April 22, 2012. The U.N. war crimes court trying Charles Taylor for atrocities in Sierra Leone will deliver its verdict on Thursday. Sierra Leone's 11-year conflict from 1991-2002 left over 50,000 dead and became a byword for gratuitous violence, especially the amputation of limbs. A decade later, the West African nation is peaceful, but among the world's poorest. It is due to hold elections in November. Picture taken April 22, 2012. REUTERS/Finbarr O'Reilly (SIERRA LEONE - Tags: BUSINESS COMMODITIES CRIME LAW POLITICS CIVIL UNREST)
ATTENTION EDITORS PICTURE 14 OF 30 FOR PACKAGE 'SIERRA LEONE AFTER CHARLES TAYLOR'

A worker is pictured next to a conveyor belt at the Ariab mine September 28, 2011. The Ariab mine in east Sudan's Red Sea state, the country's largest single gold mining operation, is run by a partnership between Sudan's government and Canada's La Mancha. Sudan plans to more than double its gold output in two years partly to help make up for a possible fall in oil revenues after the independence of its crude-oil producing south in July, Sudan's Minerals Minister Abdelbagi Gailani Ahmed said in April. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS COMMODITIES)

Heavy machinery is pictured in a quarry at the Ariab mine September 28, 2011. The Ariab mine in east Sudan's Red Sea state, the country's largest single gold mining operation, is run by a partnership between Sudan's government and Canada's La Mancha. Sudan plans to more than double its gold output in two years partly to help make up for a possible fall in oil revenues after the independence of its crude-oil producing south in July, Sudan's Minerals Minister Abdelbagi Gailani Ahmed said in April. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS COMMODITIES)

A general view shows a quarry at the Ariab mine September 28, 2011. The Ariab mine in east Sudan's Red Sea state, the country's largest single gold mining operation, is run by a partnership between Sudan's government and Canada's La Mancha. Sudan plans to more than double its gold output in two years partly to help make up for a possible fall in oil revenues after the independence of its crude-oil producing south in July, Sudan's Minerals Minister Abdelbagi Gailani Ahmed said in April. REUTERS/Mohamed Nureldin Abdallah (SUDAN - Tags: BUSINESS COMMODITIES)

A muddied prospector pans for gold in Manica Province, near the Zimbabwe border, September 17, 2010. Hundreds of miners work in individual claims rented from local landowners.
REUTERS/Goran Tomasevic (MOZAMBIQUE - Tags: SOCIETY)

A shovel scoops up earth from one of two active pits at the Taparko-Bouroum gold mine site in northern Burkina Faso March 11, 2009. Toronto Stock Exchange-listed High River Gold Mines Ltd holds 90% of SOMITA SA, the operator of the mine, and the Government of Burkina Faso the remaining 10%. The company is targeting 76,806 oz of gold for 2009, an improvement on 33,000 oz produced in 2008. Picture taken March 11, 2009. REUTERS/Katrina Manson (BURKINA FASO ENVIRONMENT BUSINESS)

A gold miner inspects a rock while digging a pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in northeastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Gold miners form a human chain while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

A gold miner catches an empty pan thrown down a human chain while digging a pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Gold miners form a human chain while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Gold miners form a human chain, passing pans of mud up a slope, then throwing the empty pans down again, while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

A gold miner scoops mud while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Gold miners form a human chain, passing pans of mud up a slope, then throwing the empty pans down again, while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in northeastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited using hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Gold miners form a human chain while digging an open pit at the Chudja mine in the Kilomoto concession near the village of Kobu, 100 km (62 miles) from Bunia in north-eastern Congo, February 23, 2009. Civil conflict in Congo has been driven for more than a decade by the violent struggle for control over the country's vast natural resources, including gold, diamonds and timber, most of which is exploited by hard manual labour. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

A Congolese boy pans for gold on a riverside at Iga Barriere, 25 kms (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo, February 16, 2009. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

A Congolese man pans for gold on a riverside at Iga Barriere, 25 kms (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo, February 16, 2009. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Boys pan for gold on a riverside at Iga Barriere, 25 km (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo February 16, 2009. REUTERS/Finbarr O'Reilly (DEMOCRATIC REPUBLIC OF CONGO)

Artisanal miners dig in an open-pit mine outside the southern Democratic Republic of Congo copper town of Lubumbashi in this February 3, 2006 file photo. Poor men and women in Ghana, ex-militia fighters in steamy eastern Congo and farmers in Peru are among those joining the ranks of illegal miners and risking their lives as they seek to profit from soaring gold prices. To match feature MINING/ILLEGAL. REUTERS/David Lewis/Files (CONGO REPUBLIC)

Mustapha Kamara, 46, washes muddy gravel in the hope of finding diamonds in Sierra Leone's eastern town of Koidu January 22, 2008. The battle for Sierra Leone's eastern diamond fields fuelled its 11-year civil war, but now the muddy pits are being returned to farming under a scheme funded by U.S. luxury jewellers Tiffany & Co. Picture taken January 22, 2008. REUTERS/Katrina Manson (SIERRA LEONE)

A villager searches for diamonds in gravel near a mine outside the village of Sam Ouandja, northeast of the Central African Republic, December 6, 2007. A year of rebellion in the northeast of the Central African Republic has stopped diamond buyers coming to the village, which is now hosting several thousand Sudanese refugees. Picture taken December 6, 2007. REUTERS/David Lewis (CENTRAL AFRICAN REPUBLIC)

Villagers dig for diamonds in a mine outside the village of Sam Ouandja, northeast of the Central African Republic, December 6, 2007. A year of rebellion in the northeast of the CAR has stopped diamond buyers coming to the village, which is now hosting several thousand Sudanese refugees. Picture taken December 6, 2007. REUTERS/David Lewis (CENTRAL AFRICAN REPUBLIC)

Labourers use wooden ramps and sea water to sift through sand to extract flakes of precious metals dumped as waste on the beach in Senegal's capital Dakar June 21, 2007. Around 50 Guinean immigrants scrape a living washing and separating out traces of silver and gold from the dust before selling it back to the jewellers to be made into rings, bracelets and necklaces for European tourists. Picture taken June 21, 2007. To match feature SENEGAL-GOLD/ REUTERS/ Finbarr O'Reilly (SENEGAL)

A labourer scoops water to rinse sand in a sluice to extract precious metals from a beach in Senegal's capital Dakar June 21, 2007. Around 50 Guinean immigrants scrape a living washing and separating out traces of silver and gold from the dust before selling it back to the jewellers to be made into rings, bracelets and necklaces for European tourists. Picture taken June 21, 2007. To match feature SENEGAL-GOLD/ REUTERS/ Finbarr O'Reilly (SENEGAL)

Labourers scoop sand in an effort to extract precious metals from a beach in Senegal's capital Dakar June 21, 2007. Around 50 Guinean immigrants scrape a living washing and separating out traces of silver and gold from the dust before selling it back to the jewellers to be made into rings, bracelets and necklaces for European tourists. Picture taken June 21, 2007. To match feature SENEGAL-GOLD/ REUTERS/ Finbarr O'Reilly (SENEGAL)

Labourers work on a diamond open cast mine near Kpetewama, some 200 kilometres south of the capital, May 15. The labourers working close to front line fighting between government backed forces and rebel Revolutionary United Front (RUF) fighters say they have not found a diamond in over a year. The United Nations accuses rebel leader Foday Sankoh's forces (RUF) - which controls the country's diamond-producing areas - of attacking peacekeepers and of holding up to 500 of its soldiers and support staff hostage inland.

DJM/FMS

A labourer, working on a diamond open cast mine near Kpetewama, some 200 kilometres south of the capital, shifts water May 15. The labourers working close to front line fighting between government backed forces and rebel Revolutionary United Front (RUF) fighters, say they have not found a diamond in over a year. The United Nations accuses rebel leader Foday Sankoh's forces (RUF) - which controls the country's diamond-producing areas - of attacking peacekeepers and of holding up to 500 of its soldiers and support staff hostage inland.

DJM/FMS