Rio Tinto braces for $2.5bn Oyu Tolgoi writedown

[caption id="attachment_805813" align="aligncenter" width="600"] At full tilt Oyu Tolgoi will account for 30% of the economy of Mongolia, a nation of just over 3 million people.[/caption] Mining giant Rio Tinto (LON, ASX:RIO) is set to take a US$2.5 billion writedown...