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Tanzanite, a rare gift of nature

December 1, 2016/ BY Frank van Poorten

Tanzanite (Zoisite group)

Special for this gemstone is that tanzanite is pleochroism. This means that the gemstone can have multiple colors in different viewing directions. For the gem is purple, blue and (burgundy) red. The gem may therefore appear from the top purple and blue from the side. The gemstone is found in East Africa in Tanzania. It is a very rare gem.

Practical information about tanzanite

With a hardness of 6.5 on the Mohs scale is tanzanite suitable to wear in jewelry. But we recommend being careful to bump it against anything. The gem will break or tear. If you want to clean your jewelry with this gem, it’s possible with lukewarm water, soap and a soft toothbrush. But watch out! The tanzanite gemstone could be damaged by ultrasonic, steam cleaning or high temperature (enlarging / reducing a ring). So do not bring your jewelry to the first best jeweler or goldsmith! The gemologist (gems expert) knows what to do with your precious Tanzanite jewelry.

Know the rules of the rock

Like the GIA (International Gemological Institute of America) diamond assesses the four C’s, the tanzanite is also been rated according to the color, clarity, cutting and carat. Of course, also here, the higher the combination of the 4C’s, the rarer and more valuable is the tanzanite gemstone.

Carat (carat)

The weight of the gem  is referred to in carat. 1 carat is 200mg. A tanzanite’s gemstone with the same dimensions in width and length can have a different weight than a same copy, as the height of the gemstone is different. If the stone is so ‘deep’ than the carat weight will be higher.

Color (color)

The price of the gem is partly determined by the color. The intensity of the gemstone is expressed in terms of Vivid to Pale (V to P). This stands for the intensity of the existing colors of blue and violet. The deeper the color, the more valuable is the tanzanite. The color of the highest quality is sapphire-blue.  In artificial light, it  looks more like amethyst violet. After processing (heating and grinding) of the stone can vary the color of beautiful deep blue to bright purple.

Purity (clarity)

The purity of the gem is expressed by flawlessness or clarity (loupe clean) to coarse inclusions (heavily included). Loupe clean means no visible inclusions (defects) are visible with a loupe 10x. Eye clean means that the stone has no visible inclusions visible to the naked eye. Tanzanite gemstones valued as lightly included have small inclusions visible to the naked eye. If the defects in the stone are larger and more noticeable, than it is quality will be moderately included. Even more inclusions in the stone, the quality will be Heavily Included.

Cutting (cut)

The better the gem is faceted (cut) the better it will sparkle and if the gem is exactly cut to proper proportions and symmetry, then this is referred to as excellent cut

Tanzanite ring with diamondsHistory of Tanzanite

550 million years ago, Tanzanite arose from the Mount Kilimanjaro in Tanzania. Yet the gemstone remained unknown to the public until 1967. In this year the stone was found the first time when they were looking for sapphire gemstones. The mineral Tanzanite belongs to the Zoisite group (named after the collector Baron von Zois). That was first discovered in 1805 on the Saualpe in Carinthia. It was named to the original finding place, Saualpete. Only since decades, quality gemstones are known in fact as Tanzanite, Thuliet and Anyoliet. Of the remaining transparent Zoisiet varieties with gemstone quality (colorless, green, and brown) are so far only individual pieces or very small quantities well-known.


A fun fact is Tanzanite which owes its name to the New York jeweler Tiffany, who was looking for a beautiful and distinct name for this particular stone.

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