Europium is a silvery-white rare earth belonging to the lanthanide group.
The metal's hardness is comparable to that of lead and it is very ductile. Europium, the most reactive of the rare earth metals, quickly oxidizes in air and resembles calcium in its reactions with water. It is also used as a dopant in laser materials. Packaged under mineral oil or ampouled under argon. It should not be stored under oil though.