The Collaborative International Dictionary of English v.0.48:

Margarite \Mar"ga*rite\, n. [L. margarita, Gr. ? a pearl; cf. F.
   marguerite.]
   1. A pearl. [Obs.] --Peacham.
      [1913 Webster]

   2. (Min.) A mineral related to the micas, but low in silica
      and yielding brittle folia with pearly luster.
      [1913 Webster]