Numbering 17 according to the International Union of Pure and Applied Chemistry (IUPAC), rare earth elements, also referred to as rare or strategic metals, are found in significant quantities in the earth’s crust, where they have accumulated over the millennium. Owing to their chemical properties, and the fact that they bond with other minerals forming compounds, rare earth elements are difficult to isolate, rendering processing costs high. Nonetheless, byproducts of rare earths are integrated into numerous industry applications.

Lanthanides

With the exceptions of scandium and yttrium (exhibiting very similar chemical properties), 15 of the 17 rare earth elements found in the Periodic Table of the Elements are lanthanides, a group ranging in atomic number from 57 (lanthanum) to 71 (lutetium).

Symbol in Periodic Table	Name (click to pronounce)	Industry Application
	Scandium	Aluminium alloys in non-structural aerospace components, sporting equipment, high-intensity discharge lamps for film industry
	Yttrium	Phosphors for use in CRT displays, electronic filters in the microwave range, doping material in industrial application lasers, superconducting materials
	Lanthanum	Key component in nickel-metal hydride batteries for hybrid vehicles, used in the production fiber optic glass, camera lenses, high refractive² index glass, lighter flints, hydrogen storage, battery-electrodes, and oil refinement processes.
	Cerium	Catalytic converters, oxidizing agent, rare earth magnet component, gas tungsten arc welding electrodes, polishing powder, glass and ceramics dye, self cleaning ovens, and petroleum refining
	Praseodymium	Alloyed with magnesium for high strength/high temperature alloys, magnets, lasers, colors in ceramics, flint
	Neodymium	Mineral dating, magnets for portable music players, high efficiency electric motors, lasers (both industrial and for inertial confinement fusion), colors in ceramics, capacitors
	Promethium	Nuclear batteries, possible uses in portable x-ray machines
	Samarium	Neutron absorber in nuclear reactors, lasers, longer lasting magnets used in older portable music players, masers, pain treatment in advanced cancers
	Europium	Doping of glass for lasers, mercury vapor lamps, phosphors in various displays, including TVs, helical fluorescent lightbulbs, LEDs
	Gadolinium	MRI contrast agent, PET scan calibration agent, high-refractive¹ index glass, industrial grade garnets, lasers, x-ray tubes, neutron absorbing material in nuclear reactors
	Terbium	Doping agent required for solid state electronic devices, actuators used in naval sonar systems and sensors, high temperature fuel cells, green phosphors (radar screens), lasers, trichromatic lighting sources
	Dysprosium	Used to make laser materials and to study chemical reactions; employed in transducers, wide-band mechanical resonators and in high-precision liquid fuel injectors; also used for hard drive platters, added to enhance the performance of neodymium magnets, and vanadium² steel
	Holmium	Has the highest magnetic strength of any element; used for solid-state lasers found in microwave equipment and for fiber optic applications; one of the colorants used for glass, providing yellow or red coloring; glass containing holmium oxide and holmium oxide solutions are used as a calibration standard for optical spectrophotometers
	Erbium	Used in sunglasses, ceramics, optical fibers, amplifies light in lasers (used in medical laser technologies for dental and skin treatments); does not oxidize as easily as other rare metals
	Thulium	Surgical lasers, portable industrial X-ray machines
	Ytterbium	Gamma ray source, infrared lasers, reducing agent
	Lutetium	Catalyst in petroleum cracking, dates meteorites

¹The refractive index is used to identify and measure solids (glasses and gemstones), liquids, and gases. Often it is used to measure the concentration of a solution.

²Vanadium is an alloy used in wide variety of applications from superconductors to ceramics. It is a steel additive which substantially increases the strength of steel and is used in several bicycle parts. When combined with oxygen, the compound can be used to protect steel from corrosion. As an aluminum and titanium alloy, it is used in jet engines. Derivative products include glass coatings and components for lithium batteries. Vanadium in trace amounts is added to some vitamins. The trace mineral's health benefits however are very much subject to debate.