Prices could hit a record $5 a pound ($11,000 a tonne) over the next four to five years, given the dearth of major new mines on the horizon and as rising impurities such as arsenic force up costs for miners, said Nelson Pizzaro, chief executive of top copper producer Codelco (IPO-CIU.L).

I remember Prospekt posting this fews months back. Where copper concentrates that's not pure enough requires purer concentrates to be mixed in order to sell.