The Collaborative International Dictionary of English v.0.48:
Hiddenite \Hid"den*ite\, n. [After W. E. Hidden.] (Min.) An emerald-green variety of spodumene found in North Carolina; lithia emerald, -- used as a gem. [1913 Webster]WordNet (r) 3.0 (2006):
hiddenite n 1: a green transparent form of the mineral spodumene used as a gemstone