What are some elements in REEs that sometimes render what would otherwise be an economic deposit uneconomic?
JH: There are contaminants that can limit the ability to conduct economic work on a deposit or even limit the ability to exploit it at all. Thorium is one of the more common contaminants that you find accompanying many rare earth element deposits. Thorium is a radioactive element that someday may have uses in the nuclear power industry but, right now, if you have enough of it in a deposit, your tailings are radioactive. You must have the appropriate permitting to store those tailings, or you’re never going to start a mine. REEs occur in many different types of deposits, but, broadly speaking, they’re either going to occur in materials like carbonitite, which as the name implies is a non-silicon-based, carbon-based material, or in silicates. Silicates, though, have often proved difficult to process. The former Soviet Union for years conducted exploration programs for every one of the resources they could find inside its borders. They had huge numbers of deposits of rare earth elements t
