Terbium is a soft, malleable, ductile, silver-gray metal.
It is one of the rare-earth metals of the lanthanide series in group IIIb of the periodic table . It does not tarnish rapidly in air. Most of the salts are colorless or white and all contain trivalent terbium. Terbium is found in gadolinite, cerite, and other rare-earth minerals and is recovered from euxenite, monazite, and zenotime. The pure metal may be produced by chemical reduction of the halide with calcium.