The Collaborative International Dictionary of English v.0.48:

Millerite \Mil"ler*ite\, n.
   A believer in the doctrine of William Miller (d. 1849), who
   taught that the end of the world and the second coming of
   Christ were at hand.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Millerite \Mil"ler*ite\, n. [From W. H. Miller, of Cambridge,
   Eng.] (Min.)
   A sulphide of nickel, commonly occurring in delicate
   capillary crystals, also in incrustations of a bronze yellow;
   -- sometimes called hair pyrites.
   [1913 Webster]

WordNet (r) 3.0 (2006):

millerite
    n 1: a yellow mineral consisting of nickel sulfide; a minor
         source of nickel