Copper Fox Metals Inc.

There's a common theme spreading across the mining industry. After years of rapid growth in which a lot of money was invested in big, undeveloped projects, the companies who sat back are now scrambling to get their hands on new, undiscovered assets.

The problem is that there just aren't that many of them around anymore. As these firms watch their reserves deplete, they get more and more frantic.

This trend has been around for some time, but you're starting to hear about it more often. Geoff Burns, chief executive officer of Pan American Silver, made mention of it on a conference call to discuss his acquisition of Minefinders on Monday. He said his firm scanned the world over and found that the opportunities for undeveloped assets are “just not out there,” he said. “At least not anywhere we’ve looked.”

A week ago, Francis McGuire of Major Drilling Group International Inc. made a similar point in an interview with the Globe. "A couple of my directors are mining executives and they say it is all about reserves dropping," he told reporter Gord Pitts. "And nobody cares about the price next year, but everybody is thinking about prices in 2018-2020."

Maybe most famously, when Barrick Gold Corp. (ABX-T46.130.180.39%) bought Equinox Minerals Ltd. for $7.3-billion in 2011, the theme was also relevant. When analysts and investors raised concerns about overpaying for the target, Barrick CEO Aaron Regent assured them that paying that much was worth it because it was rare to see such a big early stage African copper project become available.

Given that history, it will be interesting to watch as more and more miners burn their reserves. If the situation becomes grave, you might see a flurry of deals.