True. But why not use Depleted uranium? It is already purified...

True. But why not use Depleted uranium? It is already purified and costing Millions of $ to Store. Also The Mine in Africa was originally a uranium mine GWM had already made the decision to just recover REE from the original tailing while they invested in Processing. There is a mine even richer in HRRE which is now closed in Alaska. It was owned by Ucore. This was heavily supported by J Lifton. Who was Garths buddy is probably still is.
Both mines have the exact same problem. Because of the very hard rock the REE is it can only be take out by tunnel mining. Removing overburden is too expensive. The sell price just does not make a tunnel mine economical. Maybe some day but the REE prices will have to at least triple.

The Ucore PEA talks about this in detail The first couple of dozen pages say how great the mine could be. If I remember right somewhere After page 50 the hard economic assessment starts this is not very encouraging. It list many of the problems. I do not thin GWM ever published a Full PEA just a short preliminary. Do you know of one?

PS I first sailed past then I drove around one of the US storage sites in Paduch KY going to airport. This is one of 3 in US and it is huge. Want to know more about using Depleted U Check out Traveling wave reactors and Terrapower.