Erbium is a chemical element in the lanthanide series, with the symbol Er and atomic number 68. A silvery-white solid metal when artificially isolated, natural erbium is always found in chemical combination with other elements on Earth. As such, it is a rare earth element which is associated with several other rare elements in the mineral gadolinite from Ytterby in Sweden.
Pure erbium metal is soft and malleable and has a bright, silvery, metallic lustre. As with other rare-earth metals, its properties depend to a certain extent on impurities present. The metal is fairly stable in air and does not oxidise as rapidly as some of the other rare-earth metals.