Cerium is the most abundant element of the rare earth group. It ranks 28th in the abundances of the 83 naturally occurring elements of the Earth's lithosphere.
The more important minerals containing cerium are allanite (also known as orthite), bastnasite, cerite, and monazite. Allanite, which is a silicate containing rare earths, aluminum, calcium, and iron, is widely in the United States, Germany, Greenland, Madagascar, Russia and Scandinavia. Bastnasite, which is essentially a rare earth fluorocarbonate, is the second most important commercial source for cerium and the light rare earths. The major deposit of bastnasite is found in Southern California. Cerite, which is a calcium-iron-rare earth silicate, is principally found in Sweden. Although it is quite high in rare earth content, it is not abundant enough to a primary source of the light rare earths. Monazite, which is the principal source of cerium, is a phosphate containing thorium and the light rare earths. The most important deposits are located in the United States (Florida and Idaho), Australia, Brazil, India and South Africa.