Standard State: solid at 298 K
Discovered by Mosander in 1843, Terbium is a member of the lanthanide or "rare earth group of elements. It is found in cerite, gadolinite, and other minerals along with other rare earth. It is recovered commercially from monazite in which it is present to the extent of .03% from xenotime, and from euxenite, a complex oxide containing 1% of more of terbia. Terbium has been isolated only in recent years with the development of ion-exchange techniques for separating the rare-earth elements. Terbium is a silver gray metal, and is malleable ductile, and soft enough to be cut with a knife. The oxide has potential application as an activator for green phosphors used in color TV tubes.