Rare earth mines in the U.S contain almost no heavy rare earths, while 70% of the world's heavy rare earths are in other countries.The mining of domestically produced rare earths in the U.S is a method of high input and low output,it is unbalanced and can't meet diverse needs.Rare earth mines in the U.S contain almost no heavy rare earths, while 70% of the world's heavy rare earths are in other countries.The mining of domestically produced rare earths in the U.S is a method of high input and low output,it is unbalanced and can't meet diverse needs.