Global demand for rare earth resources and strategies for ...
2016-10-1 · Rare earths are actually not rare to exhibit a broad geographical distribution. The average levels of REEs in the earth''s crust range from 150 to 220 ppm (ppm) which exceed the level of many other metals mined for industrial use (e.g. copper: 55 ppm and zinc: 70 ppm) (Long et al., 2010).Nonetheless, establishing and maintaining a reliable supply chain of REEs are of great concern …