"The intriguing thing about both neodymium and cerium is that while they’re called rare earth minerals, they’re actually fairly common.
Neodymium is no rarer than copper or nickel and quite evenly distributed throughout the world’s crust. While China produces 90% of the global market’s neodymium, only 30% of the world’s deposits are located there.
Arguably, what makes it, and cerium, scarce enough to be profitable are the hugely hazardous and toxic process needed to extract them from ore and to refine them into usable products. For example, cerium is extracted by crushing mineral mixtures and dissolving them in sulphuric and nitric acid, and this has to be done on a huge industrial scale, resulting in a vast amount of poisonous waste as a byproduct.
It could be argued that China’s dominance of the rare earth market is less about geology and far more about the country’s willingness to take an environmental hit that other nations shy away from."