Lutetium was the last rare earth metal to be discovered in the mineral Ytterbia by Carl Auer von Welsbach, Charles James, and Georges Urbain. It was Urbain who successfully separated out Lutetium in 1907 using nitric acid. It exists in the earth's crust in minerals and ores and whilst rare is more abundant than gold and silver. Lutetium oxide is used in catalysts in the petroleum industry and Lu -177 the isotope is used in cancer treatments due to its radioactivity. Lutetium atoms are the smallest of all the lanthanides meaning it has the highest melting and boiling points. It is a solid metal at room temperature with a melting point of 1652°c and a boiling point of 3402°c.