Tanzanite was enthusiastically celebrated after its discovery in 1967 as "Gemstone of the 20th Century.” The only known source of Tanzanite is a five square mile hilltop at Merelani, ten miles south of the Kilimanjaro International Airport in Tanzania.
While the correct name for the gemstone is “blue Zoisite,” the New York jewelry company, Tiffany, suggested it should be named after the place in occurs on the earth because the words “blue Zoisite" sounded unfortunately too much like the word "suicide". The name Tanzanite was used and has stuck helping this beautiful gemstone achieve success in the marketplace.
The deep blue colors of Tanzanite range from ultramarine to a light purplish blue. The most coveted color is a blue which shows a purplish hue. The source of its mesmerizing color is that tanzanite is trichroic: that is, it shows different colors when viewed in different directions. One direction is blue, another purple, and another bronze, adding subtle depths to the color.
Most rough crystals show a large proportion of the brownish-yellow, but the cutter may cure this by carefully heating the stone in an oven to about 500°C. This heating process requires careful attention because it is essential to determine the moment when the color turns blue. Heating is a treatment which is generally accepted in the trade and should be expected. Due to the heating, the most desirable rough stones are those that are relatively free of inclusions so that the heating process does not lead to fissures in the stone.
Tanzanite is a blue variety of the gemstone, Zoisite (hydrated calcium aluminum silicate) which has hardness 6.5 to 7 on the Mohr’s scale. It is not very scratch resistant so must be worn with care, especially in rings.
Tanzanites should be cleaned with warm, soapy water and a soft bristle brush. It should never be cleaned by ultrasonic method and because of its chemical composition should never come into contact with acids. Never resize or repair a ring set with tanzanite because the stone could shatter in the heat of a torch.
New mining techniques and the liberalization of the Tanzanian economy has helped to boost production in the past few years to make tanzanite more available than ever before in the history of the gemstone.
Among the important gems discovered in the last 90 years, only Tanzanite has been added to the official birthstone list. It was adopted as a December birthstone by the American Gem Trade Association and shares that month with turquoise and zircon.
Tanzanites have become very popular and increasingly valuable for two obvious reasons: First of all is the spectacular color? Secondly, the stone is found on only one special location in the entire world. This is what makes it is especially valuable. The desire to own something unique and rare has always been a decisive criterion for assessing the value of special gemstones.