Turquoise is the traditional birthstone for December, Blue Zircon is the modern birthstone, but gemstone enthusiasts now accept Tanzanite as Decembers Birthstone also.
Tanzanite was discovered in the late 1960s, and is found exclusively, in Tanzania. It is treasured for,
and is often heat treated to achieve, its rich violet-blue color. Originally purchased as an alternative to Sapphire, it has increased in popularity and is now valued more for its own beauty and brilliance.
Formula: (Ca2Al3(SiO4)(Si2O7)O(OH)) + (Cr,Sr)
Color: Purple to blue
The name Turquoise is derived from the French, pierre turquoise, meaning “Turkish stone,” because the trade routes that brought Turquoise to Europe from the mines in central Asia went through Turkey, and Venetian merchants often purchased the stone in Turkish bazaars.
Turquoise varies in color from greenish blue, through robin's egg-blue, to sky blue shades and its transparency ranges from translucent to opaque.
Color: Blue, blue-green, green
Zircon is one of the heaviest gemstones; this means that it will weigh more than other stones with the same measurements.
Meanings associated with the Blue Zircon are success, love, luck, happiness and prosperity. Zircons are thought to increase intuition, durability and steadiness. Many believe that those who wear the Zircon will experience a decrease in depression and insomnia
Derived from the Arabic word zar and gun, meaning gold and color, zircon is found in a wide range of colors such as: blue, yellow, orange, brown, green, color less and the most prized red!
See more at: http://www.americangemsociety.org/december-birthstones