A bright, silvery, reactive element of the lanthanide series, found in the minerals monazite and bastnaesite and used for coloring glass, for doping laser glass and crystals, and in materials with strong, permanent magnetic properties that make them useful for computer and audio equipment. Atomic number 60; atomic weight 144.24; melting point 1,016°C; boiling point 3,074°C; specific gravity 7.008; valence 3. See Periodic Table.