Tanzanite (officially called: blue zoisite, but was renamed through marketing as it was through that "blue zoisite" might be pronounced like "blue suicide" and so wouldn't sell well) is the blue/purple variety of the mineral zoisite (a calcium aluminium hydroxy silicate) discovered in the Mererani Hills of Manyara Region of Northern Tanzania in 1967.
Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet and burgundy, depending on crystal orientation. Tanzanite can also appear different when viewed under alternate lighting conditions. The blues appear more evident when subjected to fluorescent light and the violet hues can be seen readily when viewed under incandescent illumination. Tanzanite in its rough state is usually a reddish brown colour. It requires artificial heat treatment to 600 degrees Centigrade in a gemological oven to bring out the blue violet of the stone. Tanzanite is a rare gem. It is found only in the foothills of Mount Kilimanjaro.
Emmanuel Merishiek Mollel, a Maasai tailor and part-time gold prospector living in Arusha (Tanzania) found some transparent fragments of vivid blue and blue-purple gem crystals on a ridge near Mererani, some 40km southeast of Arusha. It was some time and passed through many hands before it was correctly identified as a new gem variety of the mineral zoisite. The world's largest faceted tanzanite is 737.81 carats. One of the most famous large tanzanite's (242 carats) is the "Queen of Kilimanjaro". It is set in a tiara and accented with 803 brilliant cut tsavorite garnets and 913 brilliant cut diamonds. The piece is part of the private collection of Michael Scott, the first CEO of Apple Computers. Because it is relatively soft, tanzanite is most commonly set in necklaces and earrings.