Molycorp was active 15 years ago. As I recall, it was owned by a Canadian magnet company at the time, with talk of a big investment by US based Carlyle forthcoming, which never happened. As a small investor, it was a painful time. They could not obtain certain acids, due to conpetition from the demands of the fracking boom. At one point their bond value dropped and that was the clue to get out Now. I've worked among engineers in another field and all of the proper engineering scale up I've seen just never happened at Molycorp. I might also note here that rare earths come with radioactive impurities. That's okay, if you safely return tailings to their source, but that too complicates the engineering.