Source : Webster's Revised Unabridged Dictionary (1913)

Muscovite \Mus"co*vite\, n. [See {Muscovy glass}.]
   1. A native or inhabitant of Muscovy or ancient Russia;
      hence, a Russian.

   2. (Min.) Common potash mica. See {Mica}.

Source : WordNet®

Muscovite
     adj : of or relating to the residents of Moscow; "Muscovite street
           dealers"
     n 1: a colorless or pale brown mica with potassium
     2: a resident of Moscow