Holmium (chemical symbol Ho, atomic number 67) is a relatively soft, silvery-white metallic element that is stable in dry air at room temperature.
Like the other rare earth elements, holmium is not found as a free element in nature.
Holmium is commercially extracted by ion-exchange from monazite sand (0.05 percent holmium), but it remains difficult to separate from other rare earth elements.
Holmia was later found to be holmium oxide, and thulia was thulium oxide.
Of all the naturally occurring elements, holmium has the highest magnetic moment.
Holmium is also useful in nuclear control rods to absorb neutrons produced by nuclear fission reactions and in a certain type of laser to break up kidney stones.
Holmium is an inner transition metal (or lanthanide) that lies in period six of the periodic table, between dysprosium and erbium.
Many synthetic radioactive isotopes are known, of which the most stable one is holmium 163, with a half-life of 4,570 years.
Holmium was discovered by Marc Delafontaine and Jacques-Louis Soret in 1878, when they noticed its unique spectral bands in an absorption spectrum.