Chemically, most of the rare earth elements are trivalent. Cerium alone forms compounds with a valence of +4. Most rare earth compounds are strongly paramagnetic. An alloy composed of iron and of rare earth metals, called misch metal, is pyrophoric. When scratched it gives off sparks capable of igniting flammable gases. It is used in cigarette lighters, miners' safety lamps, and automatic gas-lighting devices. Misch metal is also used in making aluminum and magnesium alloys and some types of steel. Europium is used as a phosphor activator. In a color television tube it provides the red color seen by the viewer.

Rare earth elements are separated from other elements in a mineral by precipitation with a suitable reagent. Separation of the rare earth elements from each other by ordinary chemical means is difficult because their chemical properties are similar, and the isolation of an individual element may involve hundreds of fractional crystallizations. With the use of ion-exchange methods the separation of an individual rare earth element can be accomplished with greater ease and precision.

Oxides of the rare earth elements are called rare earths, and are found in minerals that are actually more abundant than those of some other metals, such as those in the platinum group. The principal source of rare earths is the mineral monazite. Some other rare minerals that also contain small amounts of rare earths include cerite, gadolinite, and samarskite.