Source : Webster's Revised Unabridged Dictionary (1913)

Rhinestone \Rhine"stone`\, n. [Cf. G. rheinkiesel Rhine quartz.]
   A colorless stone of high luster, made of paste. It is much
   used as an inexpensive ornament.

Source : WordNet®

rhinestone
     n : an imitation diamond made from rock crystal or glass or
         paste