The last century was fueled by oil and gas. Turner Caldwell is betting the next century runs on metals. “We’re entering a metals-driven economy,” said Caldwell, CEO and cofounder at Mariana Minerals, a software-focused mining startup. “Lithium and copper are going to be core, but our mandate needs to be broader than that. We’re starting to chase aluminum, which goes into lightweight alloys and plays a major part in the electrification of the economy. We’re looking at magnesium, nickel, cobalt, m...