 Prior to the advent of ion @-@ exchange separation technology in the 1950s , samarium had no commercial uses in pure form . However , a by @-@ product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of " Lindsay Mix " after the company that made it . This material is thought to have been used for nuclear control rods in some early nuclear reactors . Nowadays , a similar commodity product has the name " samarium @-@ europium @-@ gadolinium " ( SEG ) concentrate . It is prepared by solvent extraction from the mixed lanthanides isolated from bastnäsite ( or monazite ) . Since the heavier lanthanides have the greater affinity for the solvent used , they are easily extracted from the bulk using relatively small proportions of solvent . Not all rare @-@ earth producers who process bastnäsite do so on a large enough scale to continue onward with the separation of the components of SEG , which typically makes up only one or two percent of the original ore . Such producers will therefore be making SEG with a view to marketing it to the specialized processors . In this manner , the valuable europium content of the ore is rescued for use in phosphor manufacture . Samarium purification follows the removal of the europium . As of 2012 , being in oversupply , samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest . 
