To the left is the USGS map (click here) of the world where Rare Earth Elements can be found. The rarity is an economic assessment and not actual minerals/elements.
Rare earth elements (click here) are a set of seventeen chemical elements in the periodic table, specifically the fifteen lanthanides plus scandium and yttrium. Scandium and yttrium are considered rare earth elements since they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties. While named rare earths, they are in fact not that rare and are relatively abundant in the Earth's crust. What is unusual is to find them in quantities significant enough to support economic mineral development....
