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Home Precious stones Tanzanite


tanzanitThe name of this stone derives from its country of origin, Tanzania. Tanzanite stands alone among the families of precious stones because it does not belong to any of them. It is a variety of zoisite (cacium and aluminum silicate Ca2Al3[Si2O7] [SiO4]O [OH]), which was discovered in 1805 and is named after the philanthropist S. Zois, who financed the geological expeditions. Usually, zoisite is a non-transparent stone of green, blue, or pink color with a glassy shine. It has never been of much interest for jewelers, though sometimes it was used in different crafts.

For quite a long time, the most interesting variety of zoisite was unknown. The first tanzanite was found by Manuel D’Souza. His nickname was “Crazy Manuel,” as he spent his life in Africa looking for something unknown and “unfoundable.” The geologic exploration he conducted did not bring him much profit, so to make a living and support his family, he had to work as a tailor as well. Finally, Lady Luck smiled at him: he was going to search the region of Mount Kilimanjaro.

This place was rather far away from the future tanzanite deposit, but if it weren’t for bad luck, there would be no luck at all. The road was so bad, and the driver hired by Manuel refused to drive any further. D’Souza was left by the side of the road – exactly four kilometers from where the first tanzanite was found. At first, when D’Souza took a crystal of zoisite in his hands, he thought it was a sapphire, but he quickly realized the hardness of the crystal was far from that of a sapphire. This finding did require some additional study, but he lacked the necessary funds, so he had to continue working hard as a tailor for several more months. Later analysis showed that the stones he found were zoisites. D’Souza was surprised, as zoisites occurred quite often in Tanzania, but only the green ones--he did not know there were zoisites of another color.

Tanzanite plays blue colorTanzanite plays blue color tanzanit_01 A typical trigonal-cut tanzanite. The purple shade is clearly seenA typical trigonal-cut tanzanite. The purple shade is clearly seen

D’Souza’s luck turned even better: Tiffany’s made the decision to promote his discovery. In the 1970s, when the first Tiffany collections with this gemstone appeared, it was positioned as the imitation of sapphire. Obviously, such a low profile is not normally a suitable prerequisite for success. But the rise of the blue zoisite began when it got another name. The new name came about when Henry Platt, then president of Tiffany’s, was not happy with the word “zoisite,” which to him resembled too closely the word “suicide.” So a gemologist from Germany, Herman Bank (by the way, his son Francesco and I often traveled throughout Brazil together) coined the word “tanzanite.”

The advertisers of Tiffany grasped the idea in no time, since this new name was a perfect match for the first wave of African ethno-fashion. The smart promoters called it the “gemstone of 20th century,” and soon the newbie hit the U.S. market, which is always eager to see something new and unusual. The smart strategy of the suppliers prevented the market from being overflowed with tanzanite, letting the demand grow bigger than the supply, and as a result, tanzanite costs more than the blue sapphire it was once thought to imitate.

Today, tanzanite is quite popular and sells more than many famous stones. The trend is spreading like wildfire; this gem is valued not only in America, but also in proper and traditional Europe. It is highly possible that soon sapphires will be considered the imitations of tanzanite.

tanzanit_08 tanzanit_07

There are two major factors that explain the growing interest in tanzanite and its subsequent high prices. The first factor is its extreme rareness. Tanzanite is mined only in the Arusha province in Tanzania. While all other varieties of tanzanite are quite widespread, tanzanite occurs only here, on the Mererani plateau. Moreover, its deposits are limited and are nearing depletion. So there is some sense in buying this stone as a future rarity.

The second factor of popularity is the tanzanite’s inimitable deep blue-indigo color. As I have already mentioned, the main feature and value of tanzanite is its bright, rich, blue indigo color. Those who know gems believe it is the color of the sky above the Mount Kilimanjaro where it is mined. Others say it is simply a neon color.

The blue-lavender coloring of tanzanite is unique among jewelry stones. Its natural color varies from indigo to deep purple. When looked at from different angles, a crystal of tanzanite may look blue, burgundy, brown-yellow, or green. The two latter varieties were a problem for the jewelers who did not know what to do with such “unaesthetic” stones, but they found a way around the problem (more on this later). Tanzanite has the so-called “alexandrite effect,” which means that it changes its color depending on the light. In the electric light of a lamp, it becomes amethyst-violet; also, there is a tanzanite’s cat’s eye. This is how one can easily tell a tanzanite from sapphires, which look similar.

tanzanit_04 A ring with a large tanzaniteA ring with a large tanzanite tanzanit_06

Naturally pure indigo tanzanites are extremely rare, yet the market asks for more and more. So the way out of the dilemma was discovered by the smart Israelites. They started to change the colors of tanzanite by giving it thermal treatment. Usually, to get the needed color the green and brown stones had to be heated for two hours to 400° so they acquire the deep indigo (royal blue) color with shades of purple and lilac. Heat it too much, and the structure will lose water and the crystals’ color will turn dirty yellow. This effect is quite long lasting, but the owner should avoid the sharp temperature contrasts. This heating procedure is not described in the certificate of a stone, as it is believed there are almost no unheated tanzanites on the market.

Heating is a good remedy for the gray, unpleasant stones that occur very often. As for the blue tanzanite itself, it is still found in one place only--on that same Mererani plateau.

Large tanzanites are found quite often. Crystals weighing 30, 40, 50, and even 70 carats are not that rare. A five-carat stone from a dealer would cost $600 per carat, and for a buyer the price may rise a bit to $1000 USD per carat. The largest jewelry tanzanites ever found weigh 122.7 and 220 carats.

The color is a major component of a tanzanite's price. A royal blue color with shades of purple and lilac is the most valued--up to $1000 per carat in the 10-carat inserts. But even the best blue will always have a touch of violet. Sometimes black tanzanites are sold.

Tanzanites are given all types of cuts, but the cat’s eye stones are given only the cabochon cut. Even jewelers must be reminded that the stone is very delicate and requires a lot of attention and care during cutting and setting. Moreover, the tanzanite inserts should not be washed in the ultrasonic baths or acid environments, only in a soap solution. This gem is rather vulnerable to damage, so the jewelry pieces featuring tanzanite should not be worn daily. They are to be put on only for exceptionally important occasions, perhaps when one must showcase one’s wealth or sophisticated taste.