A huge $6.2 billion copper mine in Mongolia that could transform the sprawling nation\'s fortunes has started exports, resources giant Rio Tinto said Tuesday. The Oyu Tolgoi project in the Gobi desert, at one of the richest copper deposits in the world, has been years in development and was hit by a series of last-minute delays due to political wrangling. It is expected to produce an average of 430,000 tonnes of copper and 425,000 ounces of gold annually for 20 years, said Anglo-Australian Rio Tinto, which has majority control of the mine. The open pit section will be deep enough to stack the Great Pyramid of Giza on top of itself four times, it said in a statement. The deepest underground shaft is eight times deeper than the English Channel and the copper concentrator contains enough steel to build three Eiffel Towers. Mongolia is one of the world\'s most sparsely populated countries but is undergoing a resources boom, and the mine is vital to its economy. At the opening ceremony Tuesday mining minister Davaajav Gankhuyag said it was a \"pleasure\" to note it would increase the country\'s total exports by 30 to 40 percent. The mine will generate up to one-third of government revenue by 2019, according to previous estimates, potentially allowing Ulan Bator to spend heavily on infrastructure and education if corruption can be kept in check. Jean-Sebastien Jacques, Rio Tinto\'s chief executive for copper, said it had taken \"the vision and hard work of thousands of people to get to this point\". \"We are starting to convert the rich resources beneath the desert into real wealth and opportunity for all stakeholders, including the Mongolian people,\" he said. The outlook for copper was strong, he added, and \"with continued development, Oyu Tolgoi will generate wealth for many decades to come\". Exports from the mine were initially planned for last month but were held up by a series of disputes, including an alleged demand by the government that Rio Tinto keep all export revenue in Mongolia, prompting claims of \"resource nationalism\". Mongolian officials have denied the accusations, blaming the delays on the mine operator\'s unwillingness to disclose its sales agreements. \"The stakeholders will sort out in the nearest future every question that might lead to misunderstanding and arguments in the future,\" Gankhuyag said at the ceremony, adding that \"shared determination and trust\" was needed to reach a \"better tomorrow\". The mine has also faced objections on environmental grounds, with herders citing its potential impact on livestock due to dust. The Mongolian government has a 34 percent stake in Oyu Tolgoi while a Rio Tinto-controlled firm has the remaining 66 percent.