Holmium is a metallic element with the chemical symbol Ho, atomic number 67, and atomic weight 164.93. The element name comes from the birthplace of the discoverer. In 1878, Sorrit discovered holmium from the spectrum of erbium earth, and the following year, Clive from Sweden used chemical methods to separate holmium from erbium earth. The content of holmium in the crust is 0.000115%, and it exists together with other rare earth elements in monazite and rare earth minerals. The natural stable isotope is only holmium 165. Holmium is a silver white metal with a soft texture and ductility; Melting point 1474 ° C, boiling point 2695 ° C, density 8.7947 grams per cubic centimeter. Holmium is stable in dry air and oxidizes quickly at high temperatures; Holmium oxide is known to have the strongest paramagnetism. Ho compounds can be used as additives for new ferromagnetic materials; Holmium iodide is used to manufacture metal halide lamps - holmium lamps, and holmium lasers are also widely used in the medical field.