The Collaborative International Dictionary of English v.0.48:

Emerald \Em"er*ald\, a.
   Of a rich green color, like that of the emerald. "Emerald
   meadows." --Byron.
   [1913 Webster]

   Emerald fish (Zo["o]l.), a fish of the Gulf of Mexico
      (Gobionellus oceanicus), remarkable for the brilliant
      green and blue color of the base of the tongue; -- whence
      the name; -- called also esmeralda.

   Emerald green, a very durable pigment, of a vivid light
      green color, made from the arseniate of copper; green
      bice; Scheele's green; -- also used adjectively; as,
      emerald green crystals.

   Emerald Isle, a name given to Ireland on account of the
      brightness of its verdure.

   Emerald spodumene, or Lithia emerald. (Min.) See
      Hiddenite.

   Emerald nickel. (Min.) See Zaratite.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Emerald Isle
    n 1: an island comprising the republic of Ireland and Northern
         Ireland [syn: Ireland, Hibernia, Emerald Isle]

U.S. Gazetteer Places (2000):

Emerald Isle, NC -- U.S. town in North Carolina
   Population (2000):    3488
   Housing Units (2000): 6017
   Land area (2000):     5.242411 sq. miles (13.577781 sq. km)
   Water area (2000):    0.034833 sq. miles (0.090216 sq. km)
   Total area (2000):    5.277244 sq. miles (13.667997 sq. km)
   FIPS code:            21160
   Located within:       North Carolina (NC), FIPS 37
   Location:             34.666994 N, 77.013482 W
   ZIP Codes (1990):     28594
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Emerald Isle, NC
    Emerald Isle