Tanzanite: Prize of a Gem safari
The gemstone discoveries in East Africa in the 1960s transformed the jewelry world: new varieties, new colors, and new variations on existing species made that decade the most exciting time in the gemstone industry in our lifetimes.
But no gemstone discovered in East Africa has had more of an impact on the world gemstone market than tanzanite, a velvety blue variety of the mineral zoisite that was found for the first time in 1967 and named after the country of its birth by Tiffany & Co in New York, who introduced the gemstone to the world market in 1969.
Tanzanite is the ultimate prize of a gem safari. Its rich purples and blues often have a depth comparable to the finest sapphire. Paler tanzanite has a delicate periwinkle color like the eyes of Elizabeth Taylor. It is supremely rare, coming from only one place in the world, the Merelani Hills of Tanzania, in the shadow of Mount Kilimanjaro.
Recently, 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. And its rich dramatic color is now surprisingly affordable.
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. When tanzanite is found in the ground, the bronze color dominates. However, with gentle heating, the cutter can watch the blue color bloom and deepen in the stone.
Legend has it that the affect of heat was first discovered when some brown zoisite crystals laying on the ground with other rocks were caught in a fire set by lightning that swept through the grass covered Merelani hills northeast of Arusha. The Masai herders who drive cattle in the area noticed the beautiful blue color and picked the crystals up, becoming the first tanzanite collectors.
Choosing a Tanzanite
The color of tanzanite is most intense in sizes above ten carats. Smaller tanzanites are usually paler in color. Tanzanites which are more blue rather than purple tend to be more expensive because the crystals tend to form with the blue color axis oriented along the width of the crystal instead of the length. That means that if the cutter chooses to maximize the purity of the blue color, the stone cut from the rough will be smaller and will cost more per carat. The blue color, however, is so beautiful, that the sacrifice is often worth it.
Tanzanite jewelry is a little more delicate than other gemstone jewelry and should not be set in a ring that will be worn during strenuous activity. Never clean tanzanite in an ultrasonic cleaner or resize or repair a ring set with tanzanite because the stone could shatter in the heat of a torch. It is available in a variety of shapes and sometimes in large sizes that are perfect for an important necklace.
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