Here's a recent article talking about M&A in the copper industry. It is the first time in a long time that I've seen the buy vs. build debate tilt towards building greenfield properties. As Calvin has been saying, why would anyone sell their best assets cheaply, or even at all? That's why some of the Majors appear to be going back and looking at their potential greenfield operations.

For Rio Tinto Group, the world’s second-biggest mining company with copper assets in the U.S., Mongolia and Indonesia, a barrier to dealmaking is the expensive demands from sellers.

“We’ll keep an opportunistic view on M&A but it’s not our priority today,” Jean-Sebastien Jacques, the company’s head of copper, said in an interview Wednesday in Santiago. “You’re going to have to pay a high price for any high quality asset. The good assets are not easy to come by. I don’t think it’s going to be build versus buy. It’s going to be build and some buy.”

--http://www.bloomberg.com/news/articles/2015-04-15/copper-miners-eyeing-m-a-as-red-metal-s-scarcity-sparks-interest