gadolinia

from The Century Dictionary.

• noun In chem., oxid of gadolinium, one of the rare earths, found as a constituent of the mineral samarskite from North Carolina; also found in orthite.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Chem.) A rare earth associated with yttria and regarded as the oxide (Gd2O3) of a metallic element, gadolinium.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun chemistry, archaic A rare earth, regarded by some as an oxide of the supposed element gadolinium, by others as only a mixture of the oxides of yttrium, erbium, ytterbium, etc.