gadolinite
noun
gad·o·lin·ite ˈga-də-lə-ˌnīt 
: a black or brown mineral that is a source of rare earths and consists of a silicate especially of iron, beryllium, yttrium, cerium, and erbium
Word History
Etymology
borrowed from French, from Johan Gadolin †1852 Finnish chemist and mineralogist + -ite -ite entry 1
Note: Gadolin wrote a description of the mineral based on a sample found at the Ytterby quarry on the island of Resarö in the Stockholm Archipelago, Sweden ("Undersökning av en svart tung stenart ifrån Ytterby stenbrott i Roslagen," Kongl. Vetenskaps-Akademiens Nya Handlingar, vol. 15 [1794], pp. 137-55).
First Known Use
1801, in the meaning defined above