Source : Webster's Revised Unabridged Dictionary (1913)

Turquoise \Tur*quoise"\, Turquois \Tur*quois"\ (?; 277), n. [F.
   turquoise; cf. Pr. & Sp. turquesa, It. turchese, turchina,
   LL. turchesius, turchina; -- so called because first brought
   from Turkey. See 1st {Turkey}.] (Min.)
   A hydrous phosphate of alumina containing a little copper;
   calaite. It has a blue, or bluish green, color, and usually
   occurs in reniform masses with a botryoidal surface.
   [Formerly written also {turcois}, and {turkois}.]

   Note: Turquoise is susceptible of a high polish, and when of
         a bright blue color is much esteemed as a gem. The
         finest specimens come from Persia. It is also found in
         New Mexico and Arizona, and is regarded as identical
         with the chalchihuitl of the Mexicans.

Turquoise \Tur*quoise"\, a.
   Having a fine light blue color, like that of choice mineral
   turquoise.

Source : WordNet®

turquoise
     n 1: a blue to gray green mineral consisting of copper aluminum
          phosphate; blue turquoise is valued as a gemstone
     2: a shade of blue tinged with green [syn: {greenish blue}, {aqua},
         {aquamarine}, {cobalt blue}, {peacock blue}]