Despite the name, rare earths are actually fairly common; they are expensive and seldom mined elsewhere because the processing equipment to separate them from t

Despite the name, rare earths are actually fairly common; they are expensive and seldom mined elsewhere because the processing equipment to separate them from the ore is expensive and because rare earths almost always occur naturally in deposits mixed with radioactive thorium and uranium. Processing runs the risk of radiation leaks [...] http://en.wikipedia.org/wiki/Didymium http://en.wikipedia.org/wiki/Didymium http://en.wikipedia.org/wiki/Samarium http://en.wikipedia.org/wiki/Samarium