(Ytterby, a town in Sweden) Erbium, one of the so-called rare-earth elements on thelanthanide series, is found in the minerals mentioned under dysprosium. In 1842 Mosanderseparated "yttria" found in the mineral gadolinite, into three fractions whichhe called yttria, erbia, and terbia. The names erbia and terbia became confused in thisearly period. After 1860, Mosander's terbia was known as erbia, and after 1877, theearlier known erbia became terbia. The erbia of this period was later shown to consist offive oxides, now known as erbia, scandia, holmia, thulia and ytterbia. By 1905 Urbain andJames independently succeeded in isolating fairly pure Er2O3. Klemm and Bommer first produced reasonablypure erbium metal in 1934 by reducing the anhydrous chloride with potassium vapor. Thepure metal is soft and malleable and has a bright, silvery, metallic luster. As with otherrare-earth metals, its properties depend to a certain extent on the impurities present.The metal is fairly stable in air and does not oxidize as rapidly as some of the otherrare-earth metals. Naturally occurring erbium is a mixture of six isotopes, all of whichare stable. Nine radioactive isotopes of erbium are also recognized. Recent productiontechniques, using ion-exchange reactions, have resulted in much lower prices of therare-earth metals and their compounds in recent years. The cost of 99+% erbium metal isabout $650/kg. Erbium is finding nuclear and metallurgical uses. Added to vanadium, forexample, erbium lowers the hardness and improves workability. Most of the rare-earthoxides have sharp absorption bands in the visible, ultraviolet, and near infrared. Thisproperty, associated with the electronic structure, gives beautiful pastel colors to manyof the rare-earth salts. Erbium oxide gives a pink color and has been used as a colorantin glasses and porcelain enamel glazes.