In this mineral - later called gadolinite, after him - he had found a hitherto unknown earth, the so-called yttria.    From Wordnik.com.  [Nobel Prize in Chemistry 1951 - Presentation Speech] Reference

In 1879 a Swedish chemist named Lars Fredrik Nilson was looking for rare earth elements in the minerals euxenite and gadolinite when he discovered erbium and ytterbium; scandium was later separated from the ytterbium.    From Wordnik.com.  [Scandium] Reference

Yttria is found in gadolinite and some other rare minerals.    From Wordnik.com.  [A Text-book of Assaying: For the Use of Those Connected with Mines.] Reference

The minerals observed in these three showings are fergusonite, chevkinite, gadolinite, pyrochlore, zircon, monazite, allanite and ferrocolombite.    From Wordnik.com.  [Marketwire - Breaking News Releases] Reference

To date, a wide variety of REE-bearing minerals have been identified, including apatite, iimoriite, kainosite, gadolinite, allanite, bastnaesite, parisite, brannerite, thalenite, xenotime, fergusonite, synchysite (Y), and monazite.    From Wordnik.com.  [Marketwire - Breaking News Releases]