Holmium

Holmium is a soft, silvery rare-earth metal. It was spotted in 1878 by Marc Delafontaine and Jacques-Louis Soret, and independently in 1879 by Per Teodor Cleve, who named it after Stockholm (Latin Holmia). Like other rare earths, it is mined from minerals such as monazite and from clay deposits.

Each holmium atom is a stronger tiny magnet than the atoms of any other naturally occurring element. Engineers use holmium for the pole pieces that concentrate the fields of the strongest magnets. Crystals laced with holmium make lasers whose light is absorbed by the water in tissue, so surgeons use them to break up kidney stones and cut precisely. Holmium oxide is also a standard for calibrating instruments that measure light.