Tanzanite

Zoisite that has a blue color is called "Tanzanite".
"Merelani" in Tanzania.
This is the only place in the world where tanzanite is found.

Discovered just 50 years ago, tanzanite was named for its resemblance to the Tanzanian evening sky.
It has also been called the "gem of the 20th century" because of the beauty of its blue color, which is unlike any other gemstone. Perhaps this is because the complex blue color is created by its pleochroism, a property that allows it to show different colors depending on the angle or light.

The deeper you look, the more complex the blue color, from pale blue to light purple, the more you can imagine the sky of faraway Tanzania.

December's birthstone.