The sky's the limit when it comes to talking up the wealth beneath our land and seabed. In an influential report in March 2008, consultant geologist Richard Barker estimated the potential value of just seven minerals, including gold, copper, iron and molybdenum (used in alloys) at a mindboggling $140 billion. Throw in the Southland lignite field and there's another $100 billion. And that's just onshore resources. Barker says the rewards could be much higher.