Gemstone Education: Tanzanite: The Jewel of East Africa

Although tanzanite is a relative newcomer to the gemstone market, it has made its mark on the jewelry world in a hurry.

In fact, no recent gemstone discovery has had more of an impact. This rare, exotic gem was first discovered by Portuguese prospector Manuel¬†d’Souza in the Merelani Hills of Tanzania in 1967, in the shadow of majestic Mount Kilimanjaro. This breathtaking location is the only known mining site on earth for tanzanite. The stone was named after its country of origin by Tiffany & Co. in New York. The world-renowned jeweler first introduced tanzanite to the market in 1969 and began to aggressively market it to the public in the 1980s. Tanzanite, a variety of the mineral zoisite, occurs in a wide range of shapes, sizes and colors.

Rarely pure blue, the gem almost always displays signature overtones of purple. In smaller sizes, it tends toward lighter tones, with lavender the most common. In larger sizes, the gem typically displays deeper, richer blues and purples. It is this mesmerizing saturation of color that has made tanzanite so sought after. In 1998 and 1999, it was proclaimed the number one colored stone sold worldwide. Although demand for this beautiful gem continues to grow, supply shortages in recent years have hampered production and caused price fluctuations. In its natural form, tanzanite is typically brown with reddish, orange, yellow or bronze hues. Heat treatment releases the spectacular violet-blue colors the stone is known for. According to legend, the affect of heat on tanzanite was first discovered when some brown zoisite crystals lying on the ground among other rocks were caught in a fire started by lightning that swept through the grass-covered Merelani Hills.

Masai cattle herders in the area noticed the beautiful blue color of the crystals and picked them up, becoming the first tanzanite collectors. The finest quality tanzanite is usually deep blue or violet, with few, if any, inclusions visible under magnification. Such stones are also exceptionally well-cut and polished. But color is the most important factor to consider when buying tanzanite. The gem is usually available in four quality grades: “AAA,” “A,” “B” and “C.” “AAA” quality features the richest color and is very rare and limited. “A” quality, generally considered the highest grade available in most jewelry stores, exhibits slightly less intense color and has also become limited. “B” and “C” qualities, which exhibit increasingly lighter hues of color, are still very abundant. With a ranking of 6.5 out of 10 on the Mohs scale, tanzanite is similar in hardness to an emerald but softer than a diamond.

Although it is safe to wear tanzanite jewelry on a daily basis, avoid impacts that could crack, chip or shatter the stone. Clean your tanzanite with warm, soapy water and a soft bristle brush. Also, avoid ultrasonic or steam cleaning, because the high temperatures could damage the stone. Most nicks and scratches can be removed through polishing. Tanzanite is the recommended gem for couples celebrating their 24th wedding anniversary. A noted 122.7-carat faceted stone is on display at the Smithsonian Institution in Washington, D.C.

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