Tanzanite is the blue and also violet variety of the mineral zoisite. Belonging to the epidote group. The gemstone was discovered by Manuel d’Souza in 1967. In the Merelani Hills of Manyara Region, Northern Tanzania. Near the city of Arusha and Mount Kilimanjaro. The only source of Tanzanite is furthermore Tanzania. In a very small mining area. Approximately 7 km long and 2 km wide. Near the Mirerani Hills.
A remarkably strong trichroism is visible on Tanzanite. It appears alternately blue, and also violet. Burgundy depending on crystal orientation. It can also appear differently when viewed under alternate lighting conditions. The blues appear more evident when subjected to fluorescent light. The violet hues is easily visible when subjected to incandescent illumination. In its rough state tanzanite is sometime reddish brown. By heat treatment, it s possible to remove the brownish color. It finally brings out the blue violet of the stone.
Manuel d’Souza, a tailor and part-time gold prospector living in Arusha Tanzania. He found transparent fragments of blue and blue-purple gem crystals on a ridge near Mirerani. About 40 km southeast of Arusha. He assumed that the mineral was peridot. But after soon realizing it wasn’t, he concluded it was dumortierite. Shortly thereafter, John Saul saw the stones. A Nairobi-based consulting geologist.
Gemstone wholesaler who was then mining aquamarine in the region around Mount Kenya. Saul, who later discovered the famous ruby deposits in the Tsavo area of Kenya. He eliminates dumortierite and cordierite as possibilities. And sent samples to his father. Hyman Saul, vice president at Saks Fifth Avenue in New York.
Hyman Saul brought the samples across the street. To the Gemological Institute of America. They finally correctly identified the new gem as a variety of zoisite mineral.
Correct identification was made by mineralogists at Harvard University. Also by the British Museum, and finally by Heidelberg University. But the very first person to get the identification right was Ian McCloud. A Tanzanian government geologist based in Dodoma.
Scientifically called “blue zoisite”. The gemstone was renamed as tanzanite by Tiffany & Co. Because they wanted to capitalize on the rarity. And a single location of the gem.
From 1967, probably two million carat of tanzanite were mined in Tanzania. Finally, the Tanzanian government nationalized the mines in 1971.