December has three birthstones: tanzanite, zircon and turquoise. All of these birthstones are available in various shades of blue. Tanzanite has a rich violet-blue color, but it can vary across a range from blue to purple.
Zircon is available in many colors, including blue, orange, yellow, green, brown and red. Colorless zircon has been used as a diamond imitation.
Turquoise has a wide range of blue colors from sky blue to greenish blue, and it can be translucent to opaque. Turquoise is a favorite gemstone of the American Southwest.
Tanzanite was often purchased as a substitute for sapphire as it is less expensive. Zircon has been thought to relieve pain, according to folk wisdom.