Discovered by Mosander in 1843. It is found in cerite, gadolinite, and other minerals along with other rare earths. As with other rare earths, it can be produced by reducing the anhydrous chloride or fluoride with calcium metal in a tantalum crucible. Calcium and tantalum impurities can be removed by vacuum remelting. Other methods of isolation are possible.
Terbium is reasonably stable in air.
It is a silver-gray metal, and is malleable, ductile, and soft enough to be cut with a knife. C. Forty one isotopes and isomers are recognized. The oxide is a chocolate or dark maroon color. Sodium terbium borate is used as a laser material and emits coherent light at 0.546 um. Terbium is used to dope calcium fluoride, calcium tungstate, and strontium molybdate, used in solid-state devices.