The Collaborative International Dictionary of English v.0.48:

Wulfenite \Wul"fen*ite\, n. [So named after F. X. Wulfen, an
   Australian mineralogist.] (Min.)
   Native lead molybdate occurring in tetragonal crystals,
   usually tabular, and of a bright orange-yellow to red, gray,
   or brown color; -- also called yellow lead ore.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wulfenite
    n 1: a yellow to orange or brown mineral used as a molybdenum
         ore