The Swedish scientist Per Teodor Cleve discovered two new materials when he was working with the mineral Erbia. He discovered one green and one brown. The green ore turned out to me the oxide of Thulium. It was purified by Charles James in New Hampshire in 1911. Thullium is not very abundant on earth and exists in minerals and ores in the earths crust. Thulium is used in lasers with Yttrium and also used as the radioactive isotope Tm 170 in nuclear reactors. It is a solid metal at room temperature with a melting point of 1545°c and a boiling point of 1950°c.
Per Theodor Cleve