| Like other rare earths, this element is never found as a free element in nature but is found bound in monazite sand ores. It has historically been
very difficult and expensive to separate rare earths from each other in their ores but ion-exchange production techniques developed in the late 20th century have greatly brought
down the cost of production of all rare-earth metals and their chemical compounds. The principal commercial sources of erbium
are from the minerals xenotime and euxenite, and most recently, the ion adsorption clays of southern China. In the high-yttrium versions of these ore concentrates, yttrium is about two-thirds of the total by weight, and erbia is about 4-5%. This is enough erbium to impart a distinct pink colour
to the solution when the concentrate is dissolved in acid. This colour behavior is highly similar to what Mosander and the
other early workers in the lanthanoids would have seen, in their extracts from Ytterby gadolinite.
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Occurrence