Named for the mineral samarskite from which it is extracted, samarium was isolated and identified by de Boisbaudran is 1879. The pure metal has a silver lustre and tarnishes slowly at room conditions. It is readily magnetized and holds its magnetism extremely well. Rare earth magnets (samarium-cobalt, for example) exploit this property.
Although it is present in samarskite, commercial production of samarium is from monazite sand which can contain as much as 2.8% Sm by weight.
Stephen R. Marsden (ChemTopics)