(under the class definition) Alloy, or metallic composition which contains over 50 percent by weight of a single metal selected from scandium, yttrium, or lanthanum, through lutetium (i.e., atomic numbers 57 through 71), or wherein the total of all these metals taken together is over 50 percent by weight of the total alloy, or metallic composition.
(1) Note. Because the rare earths often occur together naturally and are not easily separated, they are often used as crude, or partially purified mixtures which have their own names e.g., misch metal, didymium, etc.
