It is a perfect day. The sun beats down from a clear blue sky as a group of travellers approach a vast pit carved out of the terracotta-coloured earth. Beneath them, men in torn T-shirts stand in muddy water poring intently over sieves.

The newcomers attract attention immediately. For one thing, one is white — a rare sight in this remote part of West Africa. They have just flown in from America, the last part of the journey a two-hour helicopter flight over the dense jungle canopy.

One of the party is Raekwon the Chef, a member of the hip-hop group the Wu-Tang Clan. Another is Paul Wall, a white rapper from Houston, Texas, who has gone into business manufacturing diamond-studded “grills” — bespoke gold sheaths that slip over the front teeth.

Rae and Paul are involved in a film about hip-hop and diamonds, Bling: A Planet Rock, being made for the MTV-owned music channel VH1, and they are just beginning to discover the human cost of the diamond business. In a dark twist on reality TV shows such as Faking It, VH1 has brought them to the Kono district of Sierra Leone, to confront the reality of life in one of the region’s many open-cast mines.

Conditions are abysmal: the men work in parasite-ridden water for a pittance. Many miners will be lucky to earn more than a cup of rice for their day’s work; and if they manage to find one of those rough stones in their gravel pan, they will be paid only a tiny fraction of what the cut diamond will be sold for in the West.

Rae, who will later weep at what he has seen, at one point shows off a diamond necklace he is wearing to some of the curious miners. Perhaps not really knowing what else to say, he thanks them for the work they do that enables him to wear it.

“Ninety per cent of Sierra Leoneans have never seen a diamond, let alone a polished one,” explains the journalist and film-maker Raquel Cepada, who brought the rappers to Kono. “The miners were rushing over to Rae’s necklace, inspecting it, saying ‘What? This is a diamond?’ It’s a very big deal to them that someone came all the way here to thank them for their labour. It was an incredible moment, a real culture clash.”

While the miners of Sierra Leone may be poorly paid, at least they work for themselves. Not long ago they were working at the end of a gun barrel. In 1998 a British campaigning organisation, Global Witness, first told the world about conflict or blood diamonds: stones that were being sold by paramilitary groups to help to fund their wars.

In Sierra Leone, one of the worst cases, a group called the Revolutionary United Front took over Kono and other mining districts in the 1990s, and began selling the diamonds to Western dealers for cash or weaponry.

Any miner suspected of stealing a diamond was summarily executed by RUF soldiers, many of whom were themselves forced conscripts. After an election that the RUF refused to contest, Sierra Leone’s president, Ahmad Tejan Kabbah, called for his people to “join hands”. In response the militia chopped off the hands of civilians, delivering buckets of them to the presidential offices in the capital, Freetown.

While the end of several African conflicts and new measures designed to combat the illicit trade in rough stones have helped to stem the flow of conflict diamonds to a trickle, the issue has never been more highprofile. Blood Diamond, a big-budget Hollywood drama starring Leonardo DiCaprio, Djimon Hounsou and Jennifer Connelly, set in Sierra Leone in 1999, opens in the UK on Friday.

Ed Zwick’s film portrays RUF combatants with an enthusiasm for hardcore rap equal to the rappers’ love of diamonds. In Kono, Rae and Paul encounter some familiar faces: 50 Cent, Eminem and the late Tupac Shakur all scowl back at them from miners’ T-shirts. No wonder stars feel they must take a stand.

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