The Collaborative International Dictionary of English v.0.48:

Greenockite \Green"ock*ite\, n. [Named after Lord Greenock.]
   (Min.)
   Native cadmium sulphide, a mineral occurring in yellow
   hexagonal crystals, also as an earthy incrustation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

greenockite
    n 1: ore of cadmium; a rare yellowish mineral consisting of
         cadmium sulphide in crystalline form [syn: greenockite,
         cadmium sulphide]