GEMSTONES
TANZANITE
Millions of years in the making, deep-violet tanzanite revealed itself to humans only thirty years ago. Read about this newest discovery.
THE ABCS OF TANZANITE
Tanzanite, a relative newcomer to the market, may lack in rich gem legend and lore, but it has rapidly won the public's favor since its discovery some 30 years ago.
No recent gemstone discovery has had more of an impact on the world gemstone market than tanzanite. Portuguese prospector Manuel d'Souza discovered this gem in Tanzania in 1967 while searching for sapphire. Tanzanite was named after its country of origin by Henry Platt, vice president of Tiffany & Co. in New York, one of the world's most influential jewelers who began an aggressive marketing campaign to introduce tanzanite to the public in the 1980s.
Tanzanite's mass appeal lies in its great color, a mixture of two gem favorites: sapphire and amethyst. Popular for its rich violet blue to purple tones, tanzanite has tonal depth comparable to sapphire. Rarely found in a pure blue, tanzanite almost always displays purple overtones. It is highly tri-chroic; that is, it shows varying amounts of blue and violet in incandescent light and daylight. In small sizes, tanzanite tends toward the lighter tones (lavender is most common). Tanzanite crystals naturally occur in various colors: yellow, golden brown green and blue (but rarely).
Tanzanite is a velvety-blue to purple variety of the mineral zoisite, a silicate of calcium and aluminum. Prior to its discovery, the only variety of zoisite used for gems was a pink-colored gem known as thulite. A green variety of zoisite was recently discovered which is called chrome (or green) tanzanite, owing its color to chromium.
On the Mohs scale of hardness, tanzanite ranks 6-7. This gem is considered relatively soft and thought should be given when designing jewelry to protecting the stone from harsh wear. Although its dispersion is low at 0.019, tanzanite has a moderate luster. Large stones up to 50 carats are available however, the larger the gem the more saturated the color. Limited quantities of natural gem-quality tanzanite are found almost exclusively in Arusha, Tanzania.
Warm soapy water and a soft brush is your best bet to clean tanzanite. Do not use an ultrasonic or steam cleaner. Avoid contact with acids and sudden temperature changes (as may occur in some jewelry repair and design work). It is important to buy fine tanzanite from a reputable retailer who will provide, in writing, all pertinent information regarding the gem including enhancements and special care notes.
Although it is not a birthstone, tanzanite is a recommended gift for couples celebrating their 24th wedding anniversary, according to contemporary jewelers' anniversary gemstone lists. A noted 122.7-carat faceted tanzanite is on display at the Smithsonian Institution.
BUYING TANZANITE
Color is the most important factor when considering the value of tanzanite. Tanzanite's finest color is usually strong blue as seen in daylight. Very light or dark shades are usually less valuable, but not necessarily less appealing. Beauty is in the eye of the beholder and color preferences are subjective.
Of course, clarity, cut and carat weight factor into the cost of a gem. A fine tanzanite is usually eye clean with very high clarity under magnification (few inclusions). Tanzanite prices fluctuate based on its erratic production (it's about 20%-40% less per carat than sapphire). Tanzania's mining industry presently lacks the sophisticated equipment and financing it needs to upgrade operations and increase production to meet the enormous demand for tanzanite.
Tanzanite rarely occurs as a blue stone in nature, but more often as golden brown. A majority of tanzanite on the market is heated to enhance its color to a vivid violet blue. The result of this enhancement method is permanent and stable. In recent years, tanzanite simulants have entered the market (such as violet-blue synthetic sapphire), but no synthetic tanzanite (mimicking its natural counterpart in chemical composition) has been introduced thus far.
TANZANITE HISTORY
Tanzanite is one of the more recently discovered gemstones. In July of 1967 a tailor named Manuel d'Souza from the Indian province of Goa prospecting for rubies was led to a deposit of blue stones by Maasai tribesmen. (Granted, this means the Maasai discovered it, but few places or things are considered "discovered" until a foreigner names, promotes and markets them.)
D'Souza initially believed he had stumbled upon sapphire, but found that the material was too soft to be corundum. Laboratory investigation showed that the stone was a previously unseen variety of zoisite, already known in its green form. He registered four claims with the mining office. Hot on his heels was a former Greek army officer named Papanicholau who was already involved in several gem ventures in East Africa. The area, which became known as Merelani Hill, swiftly became riddled with mines.
D'Souza was unable to maintain close control over his claims and by his own estimate up to 80 percent of his gems were stolen from him before he even set eyes on them. Undiscouraged, he hooked up with an African mine owner named Alli Juyawata, and shortly after they were joined by Papanicholau. This partnership was short-lived, ending in acrimony and court action.
The Tanzanian government took control of the mines in 1971, under the name Tanzanian Gemstone Industries, and they were turned over to the State Mining Corporation in 1976, whose methods saw reduced production. By the end of the 70s, Tiffany's, which had named and promoted the stone, stopped purchasing it because the supply was not dependable.
In the late 80s, the Tanzanian government lost control of the area, and thousands of illegal miners flocked in, but by 1991 the government regained control and has since been issuing licenses to private domestic concerns. Supply is growing, though nowhere near the levels it could be. Because the government seeks to avoid the large-scale exploitation that would result from foreign investors, much of the world's Tanzanite remains, for the time being, in the ground.