Chile's Codelco managed to renegotiate a contract signed with China's Minmetals based on the 2005 copper price.

Minería Chilena reports the deal signed in 2006 by the state run copper giant was for 55,750 tonnes of copper per year for a "privileged price" for a period of 15 years.

Copper was trading around $1.50 a pound at the time versus a market price of roughly $3.60 today – the tonnage  is now worth $450 million versus $183 million seven years ago.

The Santiago-based company reportedly lowered its premium for Chinese buyers to $100 a tonne this year from $110 in 2012, the second year it has cut its levy over spot to cover shipping and insurance .

Codelco is by far the globe's largest copper producer with annual output of 1.7 million tonnes forecast for this year.

The company is also planning to invest $5 billion this year to increase production to 2.5 million tonnes by 2021.