demantoid
noun
dem·an·toid ˈde-mən-ˌtȯid 
: a green variety of garnet used as a gem
Example Sentences
Recent Examples on the Web The surprise is a platinum basket full of anemones and flowers made of gold and demantoid garnets, and studded with 1,378 diamonds. 
Nancy Gould Chuda, Town & Country, 11 June 2021
Nancy Gould Chuda, Town & Country, 11 June 2021 Word History
Etymology
German, from obsolete German Demant diamond, from Middle High German diemant, from Old French diamant — more at diamond
First Known Use
circa 1890, in the meaning defined above