Source : Webster's Revised Unabridged Dictionary (1913)

Ruby \Ru"by\, n.; pl. {Rubies}. [F. rubis (cf. Pr. robi), LL.
   rubinus, robinus, fr. L. rubeus red, reddish, akin to ruber.
   See {Rouge}, {red}.]
   1. (Min.) A precious stone of a carmine red color, sometimes
      verging to violet, or intermediate between carmine and
      hyacinth red. It is a red crystallized variety of
      corundum.

   Note: Besides the true or Oriental ruby above defined, there
         are the balas ruby, or ruby spinel, a red variety of
         spinel, and the rock ruby, a red variety of garnet.