Digging deep in S.Africa as diamond hunt gets tougher Proof that diamonds are getting harder to find can be found in the South African bush, where one of the world's largest mining companies is spending $2 billion tunnelling beneath an open-pit mine. De Beers spent 20 years digging a 450-metres (1,500 feet) deep hole to access diamond-rich rock from the surface at the Venetia mine, close to the border with Zimbabwe and Botswana. IMAGES AND SOUNDBITES