"If we could recycle some of this waste and get something out of it that was waste years ago that isn't waste today, that certainly is a goal," said Alan Koenig, the USGS scientist in charge of the tailings project.
One sample collected in 1870 from an area near Sparks, Nev., where miners had searched for a viable copper vein, has shown promise and has given researchers clues in the search for more. They have found that some rare earths exist with minerals they had not previously known occur together.
"The copper mine never went into production, but now after all of this time we've analyzed it and it came back high with Indium, which is used in photovoltaic panels. It never economically produced copper, but it gives us insight into some associations we didn't previously recognize," Koenig said.
Indium also has been found in the defunct copper mine that dominates the artsy southern Arizona town of Bisbee.Koenig and his colleagues are working to understand the composition of all of the nation's major deposits sampled over the past 150 years. In some cases, the mines were depleted of gold or copper, but the rocks left piled alongside mines and pits could hold a modern mother lode. "We're revisiting history," he said. They are compiling data from 2,500 samples to better understand whether it's possible to predict where rare earths might be hiding based on the presence of other elements there, too. "If I had to venture a number, I'd say we have found several dozen new locations that are elevated in one or more critical metals," Koenig said. "With this project the goal would be to have this large data base available that would allow us to predict and to form new associations." Currently there is only one U.S. mine producing rare earthsâ¿¿ at Mountain Pass in the Southern California desert. Molycorp Inc.'s goal in reopening the defunct mine is 20,000 metric tons of rare earth elements by this summer, including cerium oxide used to polish telescope lenses and other glass.