Terbium is named for the village of Ytterby in Sweden and was discovered in 1843. Terbium is found along with the other rare-earth minerals principally in monazite and bastnasite. The metal is isolated using ion exchange and solvent extraction methods. Terbium, like the other rare-earth metals, has a bright silver luster and is malleable and ductile. Terbium is widely used as a phosphor activator in color tv tubes. It is also used as a doping agent for calcium fluoride, calcium tungstate and strontium molybdate, used in solid state devices.