Certain absorption bands at the blue end of the spectrum are supposed to be due to rare elements such as samarium.
samarium sa·mar·i·um (sə-mâr'ē-əm, -mār'-)
A metallic rare-earth element used in ferromagnetic alloys, 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 1,790°C; specific gravity 7.52; valence 2, 3.
A silvery-white metallic element of the lanthanide series that exists in several forms and has seven naturally occurring isotopes. It is used to make glass that absorbs infrared light and to absorb neutrons in the fuel rods of nuclear reactors. Atomic number 62; atomic weight 150.36; melting point 1,072°C; boiling point 1,791°C; specific gravity approximately 7.50; valence 2, 3. See Periodic Table.