The Collaborative International Dictionary of English v.0.48:

Jet \Jet\, n. [OF. jet, jayet, F. ja["i]et, jais, L. gagates,
   fr. Gr. ?; -- so called from ? or ?, a town and river in
   Lycia.] [written also jeat, jayet.] (Min.)
   A variety of lignite, of a very compact texture and velvet
   black color, susceptible of a good polish, and often wrought
   into mourning jewelry, toys, buttons, etc. Formerly called
   also black amber.
   [1913 Webster]

   Jet ant (Zool.), a blackish European ant (Formica
      fuliginosa), which builds its nest of a paperlike
      material in the trunks of trees.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Amber \Am"ber\ ([a^]m"b[~e]r), n. [OE. aumbre, F. ambre, Sp.
   ['a]mbar, and with the Ar. article, al['a]mbar, fr. Ar.
   'anbar ambergris.]
   1. (Min.) A yellowish translucent resin resembling copal,
      found as a fossil in alluvial soils, with beds of lignite,
      or on the seashore in many places. It takes a fine polish,
      and is used for pipe mouthpieces, beads, etc., and as a
      basis for a fine varnish. By friction, it becomes strongly
      electric.
      [1913 Webster]

   Note: Amber is classified as a fossil resin, being typically
         of ancient origin, having solidified from the exudates
         of certain trees millions of years ago. Many pieces are
         found with insects embedded, the insects having been
         trapped by the resin while they were alive. The insects
         are often very well preserved, due to the antimicrobial
         action of components of the amber. It typically
         contains from 5 to 8 percent of succinic acid. "Baltic
         amber" has been mined for centuries in the region of
         Poland formerly called East Prussia, and is the variety
         used in most jewelry made in Poland and Russia. The
         Baltic strata containing amber extend under the sea,
         and amber beads may be found there deposited by waves
         along the shore. Amber was known to the ancient Greeks.
         The name "electron" comes from the Latin word for
         amber, electrum, derived from the Greek word,
         'h`lektron (see electric), due to the electric charge
         that amber takes when rubbed, as with cat fur. Although
         at one time used in fine varnishes, it no longer has
         any commercial value for that purpose, being used
         mostly in jewelry. Significant deposits are also found
         in the Carribean region, and smaller amounts in various
         other places. The notion, that DNA sufficiently intact
         to recreate extinct animals might be extracted from
         amber, was the basis for Michael Crichton's novel
         "Jurassic Park", but has as yet (1997) not been
         demonstrated to be possible.
         [PJC]

   2. Amber color, or anything amber-colored; a clear light
      yellow; as, the amber of the sky.
      [1913 Webster]

   3. Ambergris. [Obs.]
      [1913 Webster]

            You that smell of amber at my charge. --Beau. & Fl.
      [1913 Webster]

   4. The balsam, liquidambar.
      [1913 Webster]

   Black amber, and old and popular name for jet.
      [1913 Webster]