Erbium 's a chemical element with the symbol Er and atomic number 68. A rare, silvery, white metallic lanthanide, erbium's solid in its normal state. It's a rare earth element associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden. Characteristics A trivalent element, pure erbium metal's malleable (or easily shaped), soft yet stable in air, and doesn't oxidize as quickly as some other rare-earth metals. Its salts are rose-colored, and the element has chara… (More on Erbium)