The Collaborative International Dictionary of English v.0.48:

Amethyst \Am"e*thyst\, [F. ametiste, amatiste, F. am['e]thyste,
   L. amethystus, fr. Gr. ? without drunkenness; as a noun, a
   remedy for drunkenness, the amethyst, supposed to have this
   power; 'a priv. + ? to be drunken, ? strong drink, wine. See
   Mead.]
   [1913 Webster]
   1. (Min.) A variety of crystallized quartz, of a purple or
      bluish violet color, of different shades. It is much used
      as a jeweler's stone.
      [1913 Webster]

   Oriental amethyst, the violet-blue variety of transparent
      crystallized corundum or sapphire.
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   2. (Her.) A purple color in a nobleman's escutcheon, or coat
      of arms.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Corundum \Co*run"dum\ (k[-o]*r[u^]n"d[u^]m), n.; pl. Corundums
   (k[-o]*r[u^]n"d[u^]mz). [Also corindon.] [From Hind. kurand
   corundum stone.] (Min.)
   The mineral alumina (Al2O3), as found native in a
   crystalline state. Transparent varieties are used as
   gemstones, including sapphire, which is the fine blue
   variety; the oriental ruby, or red sapphire; the oriental
   amethyst, or purple sapphire; and adamantine spar, the
   hair-brown variety. It is the hardest substance found native,
   next to the diamond.
   [1913 Webster +PJC]

   Note: The name corundum is sometimes restricted to the
         non-transparent or coarser kinds. Emery is a
         dark-colored granular variety, usually admixed with
         magnetic iron ore.
         [1913 Webster]