Mountain Pass mine of Molycorp has been discussed here many times as a likely processor of REE that MAY be produced from various projects in Arizona's Cochise County, including, perhaps, Hay Mountain.
Molycorp went bust, and a Chinese firm just bought it, subject to regulatory approval, which may be tough given the present administration in DC. That's because Mountain Pass is the only processor of REEs in the US at this time, and China is already the world's leading producer.
To my mind, allowing China to control Mountain Pass assures them a continuing strategic advantage in control of REE supplies. Maybe Obama would have approved, but ...
VP
http://www.mining.com/mountain-pass-sells-20-5-million/