Rare Earth Elements: A Beginner's Guide

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"There are only a few carbonatite deposits of commercial significance in the world."

Rare earth elements consist of a group of 15 metals. In most cases, these 15 elements are oxides. The elements are: Cerium, Dysprosium, Erbium, Europium, Gadolinium, Holmium, Lanthanum, Lutetium, Neodymium, Praseodymium, Samarium, Terbium, Thulium, Ytterbium, and Yttrium.

Most of the world's supply of rare earth elements comes from the mineral bastnasite. Bastnasite is a mixed lanthanide fluoro-carbonate mineral (Ln F CO3) that is found in rocks called carbonatites.

Carbonatites are igneous carbonate rocks (i.e., rock masses contain more than 50% carbonate minerals, and cooled from a melt). It is believed that carbonatites are carbonate rocks that were buried deep enough to melt via metamorphic processes or in the presence of igneous intrusions.

Structurally, carbonatites occur as volcanic plugs, dikes and cone sheets. They often occur as smaller components of large igneous intrusions of silicate rocks, such as nepheline syenite. In these cases the general term is to refer to a "carbonatite complex."

According to the geological literature, there are about 330 known occurrences of carbonatites worldwide, but almost all are small and noncommercial. There are only a few carbonatite deposits of commercial significance in the world.

Major Uses of Rare Earth Elements

Lanthanum
comes from bastnasite—extracted via a method called "solvent extraction"—and is a strategically important rare earth element due to its activity in catalysts that are critical in petroleum refining.

Cerium is the most abundant of the rare earth elements, and is is critical in the manufacture of environmental protection and pollution-control systems from automobiles to oil refineries.

Neodymium is a critical component of strong permanent magnets. It is used in cell phones, portable CD players, computers and most modern sound systems.

Europium offers exceptional properties of photon emission, which creates the perfect red phosphors used in color televisions and computer screens.

Praseodymium comprises just 4% of the lanthanide content of bastnasite, and is used as a common coloring pigment (in photographic filters, airport signal lenses, welder's glasses, ceramic tile and glass [usually yellow]).

Yttrium is rare in bastnasite, so is usually recovered from even more obscure minerals and ores. Almost every vehicle on the road contains yttrium-based materials that improve the fuel efficiency of the engine.

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