Blue zoisite is called Tanzanite and occurs in only one place in the world, Tanzania.   Due to its low hardness, tanzanite should always be worn carefully, it is a brittle stone.  Tanzanite is polychromatic, so depending on the angle you view from the stone can appear blue, purple, or brownish-yellow.   Most raw tanzanite occurs in brownish-yellow colours, which is then heated to achieve the desired blue-violet colour we love so much.