Tanzanite is the name given to the rich blue-violet variety of the epidote-group mineral, zoisite. The gem was first discovered in Tanzania in 1967 and was named after its country of its origin, Tanzania, by the famous New York jeweler, Louis Comfort Tiffany. Tanzanite has only one source: the hills of Merelani, near Mount Kilimanjaro, in northern Tanzania.
Tanzanite is an extraordinary mineral because it gives off a wonderful hue, most notably deep blue with a hint of purple. However it can come in other colors as well including purple or brownish yellow. Some Tanzanite even include a trichromism effect, meaning they can reflect three different colors depending on the angle which you look at the stone.
Tanzanite is relatively hard, but wearers should be cautious when wearing it in a ring setting. Because Tanzanite only has a hardness of 6.5 to 7 it can be cracked upon direct impact, it should also stay away from intense heat and even sonic baths. However, for normal wear Tanzanite is usually fine and you can’t match its beautiful purple and blue colors.
COLOR: Blue to violet to bluish purple
REFRACTIVE INDEX: 1.691 to 1.700
BIREFRINGENCE: 0.008 to 0.013
SPECIFIC GRAVITY: 3.35
MOHS HARDNESS: 6 to 7