Crossword clue: an elementary substance which forms one of the constituents of didymium. symbol nd. atomic weight 140.8.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
a yellow trivalent metallic element of the rare earth group; occurs in monazite and bastnasite in association with ceriu