is the blue/violet variety of the mineral zoisite (a calcium aluminum hydroxyl Sorosilicate) belonging to the epidote group. It was discovered by a Tanzanian Jumanne Mhero Ngoma in the Mererani Hills of Manyara Region in Northern Tanzania in 1967, near the city of Arusha and Mount Kilimanjaro. Naturally formed tanzanite is extremely rare and is endemic only to the Mererani Hills.
is noted for its remarkably strong trichroic properties, appearing alternately sapphire blue, violet and burgundy depending on crystal orientation. Tanzanite can also appear differently 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.
The largest tanzanite crystal “The Mawenzi,” was found in 2005 and crystal weighed 16,839 carats.