A silvery or pale gray metallic element of the lanthanide series found in the minerals monazite and bastnaesite and used as a dopant for laser materials, in infrared absorbing glass, and as a neutron absorber in certain nuclear reactors. Atomic number 62; atomic weight 150.36; melting point 1,072°C; boiling point 1,794°C; specific gravity (approximately) 7.520 (25°C); valence 2, 3. See Periodic Table.