A silvery, malleable metallic element that is found in the same ores as other rare-earth elements and is used in various metallurgical applications, notably to increase the strength of magnesium and aluminum alloys. Its oxide and other compounds are useful as phosphors, microwave filters, laser dopants, and superconducting materials. Atomic number 39; atomic weight 88.906; melting point 1,522°C; boiling point 3,345°C; specific gravity 4.469 (at 25°C); valence 3. See Periodic Table.