An Etymological Dictionary of Astronomy and Astrophysics

A soft, malleable, ductile, lustrous silver-white metal; symbol Tm. Atomic number 69; atomic weight 168.9342; melting point about 1,545°C; boiling point 1,947°C; specific gravity 9.3.
Thulium was discovered in 1879 by the Swedish chemist Per Theodor Cleve in a sample of erbium mineral. It was first isolated by the American chemist Charles James in 1911.

See also: From Thule, the earliest name for Scandinavia.