What does "turquoise" mean?

Turquoise: 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.