Coal could become too valuable to burn. Randall Atkins, the CEO of Ramaco Resources , found out to his surprise earlier this year that a Wyoming coal mine he purchased for just $2 million may contain the largest unconventional deposit of rare earth elements ever discovered in the United States. A third of the Brook Mine in Sheridan alone is estimated to contain up to 1.2 million tons of rare earth oxides, according to Weir International, a mining consultancy hired by Ramaco. To put that in perspective, the U.S. consumed about 10,000 tons of rare earth elements annually over the…