Turquoise, the traditional birthstone for people born in December.
It is also the Gemstone celebrated for the 5th and 11th Wedding Anniversary.
Turquoise, along with Lapis Lazuli, is one of the oldest gemstone materials known to man.
The color of turquoise is so unique that this has become the standard word we use to describe the slightly greenish shade of cyan and similar colors.
Turquoise is composed of hydrous phosphate of copper. Turquoise is always opaque and the color varies from blue to green, sometimes with flecks of pyrite or interspersed with dark, spidery limonite veining.
You can read more about the Meaning of Turquoise here.