Samarium occurs in Samarskite, which is contained in rare earth bearing granite pegmatites.
The main application of samarium is in samarium-cobalt magnets which have permanent magnetization second only to neodymium magnets; however, samarium compounds can withstand significantly higher temperatures, above 700 °C, without losing their magnetic properties. It is also used in lasers as a neutron absorber in nuclear power reactor control rods.
Samarium oxide is also used in infrared and optical glass to absorb infrared radiation. It is a catalyst for alcohols to aldehydes and ketones.
Radioactive isotope samarium-153 is the major component of the drug samarium (153Sm) lexidronam (Quadramet) which kills cancer cells in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma. Measurements of samarium and neodymium isotopic ratios are used for geological dating of rocks and meteorites.