Erbium is one of the cheaper members of the REE family. At one point in 2018 a kilogram cost as little as $100 (nearly a tenth the price of silver for comparison). This crystalline version, ten times purer than the standard grade, costs well over ten times that but we can credit market demand for this pricing asymmetry more than the added difficulty of the extra refining.

Visually, erbium is nearly identical to its cousins dysprosium and holmium both in terms of its extreme neutral grayness and the patterning of its filamentous growths. The one salient distinguishing feature is its relatively low tolerance to corrosion. In open air erbium slowly oxidizes and sheds powdery flecks that unlike nearly every other metal still obstinately refuses to gain any hint of color!