Source : Webster's Revised Unabridged Dictionary (1913)

Agate \A*gate"\, adv. [Pref. a- on + gate way.]
   On the way; agoing; as, to be agate; to set the bells agate.
   [Obs.] --Cotgrave.

Agate \Ag"ate\, n. [F. agate, It. agata, L. achates, fr. Gr. ?.]
   1. (Min.) A semipellucid, uncrystallized variety of quartz,
      presenting various tints in the same specimen. Its colors
      are delicately arranged in stripes or bands, or blended in
      clouds.

   Note: The fortification agate, or Scotch pebble, the moss
         agate, the clouded agate, etc., are familiar varieties.

   2. (Print.) A kind of type, larger than pearl and smaller
      than nonpareil; in England called ruby.

   Note: This line is printed in the type called agate.

   3. A diminutive person; so called in allusion to the small
      figures cut in agate for rings and seals. [Obs.] --Shak.

   4. A tool used by gold-wire drawers, bookbinders, etc.; -- so
      called from the agate fixed in it for burnishing.

Source : WordNet®

agate
     n : an impure form of quartz consisting of banded chalcedony;
         used as a gemstone and for making mortars and pestles