Lanthanides (elements 57–71) are fairly abundant in the earth’s crust, despite their historic characterization as rare earth elements. Thulium, the rarest naturally occurring lanthanide, is more common in the earth’s crust than silver. There are 17 rare earth elements, consisting of the 15 lanthanides plus scandium and yttrium. They are rare because they were once difficult to extract economically, so it was rare to have a pure sample; due to similar chemical properties, it is difficult to separate anyone lanthanide from the others. However, newer separation methods, such as ion exchange resins similar to those found in home water softeners, make the separation of these elements easier and more economical. Most ores that contain these elements have low concentrations of all the rare earth elements mixed.

The commercial applications of lanthanides are growing rapidly. For example, europium is important in flat-screen displays found in computer monitors, cell phones, and televisions. Neodymium is useful in laptop hard drives and in the processes that convert crude oil into gasoline. Holmium helps in dental and medical equipment. Also, many alternative energy technologies rely heavily on lanthanides. Neodymium and dysprosium are key components of hybrid vehicle engines and the magnets used in wind turbines.