The Oyu Tolgoi mine in Mongolia's freezing Gobi Desert is one of the the world's biggest - extracting a vast seam of copper, gold and silver the size of Manhattan. It's turned this country of camel and yak herders into the world's fastest growing economy. Fancy boutiques, top-end car dealerships and coffee shops are springing up across the capital. But, as Justin Rowlatt discovers, riding the boom is not easy. He meets a rapper who says the government is simply selling the country's assets to its old rival, China. And there are fears from foreign investors about attempts by the government to increase its income from the Oyu Tolgoi mine. Can Mongolia become prosperous while sharing its new-found wealth - or will it kill the goose before it has laid any gold (or copper) eggs?