No commercial metals are so scarce as a group of 15 known as the "rare earths." They are so rare, in fact, that there is some question as to whether one of them exists at all. They have tongue-twisting names (praseodymium, gadolinium, cerium, lanthanum, ytterbium, etc.), are found in rare mineral deposits, mostly in India and Brazil. Until recently, the metals had limited uses.
In the jet and atom age, these rare-earth metals have suddenly come into new importance, have sent companies scrambling for new sources. Cerium, for example, combines with magnesium and aluminum to make tough, light, heat-resistant alloys...
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