An Alaskan mine that may contain more than $500 billion in gold, copper and other minerals will never get dug if environmentalists get their way. The proposed Pebble Mine, near the headwaters of Bristol Bay in southwest Alaska, could yield a staggering 107 million ounces of gold, 80 billion pounds of copper and 5.6 billion pounds of molybdenum, which is used to make steel alloys. Pebble Partnership, which wants to do the digging, is so confident of the bounty beneath the ground it has spent five years and $107 million monitoring the soil, water and air in order to assure...