The Collaborative International Dictionary of English v.0.48:
Zinkenite \Zink"en*ite\ (-en*[imac]t), n. [From Zinken, director at one time of the Hanoverian mines.] (Min.) A steel-gray metallic mineral, a sulphide of antimony and lead. [1913 Webster]WordNet (r) 3.0 (2006):
zinkenite n 1: a steel grey metallic mineral (a sulphide of lead and antimony)