- By Julia Littlewood
- Published 04/20/2012
Tanzanite is not only highly prized for its brilliant colour which ranges from light violet blue to ultramarine blue and with a delicate hint of purple, but also for its rarity – this unforgettable semi-precious stone can only be found in the country of Tanzania, Eastern Africa.
Called the “gemstone of the 20th century”, tanzanite is today is one of the most sought after stones for use in creating breathtakingly beautiful adornments.
The following guide will give jewellery enthusiasts a comprehensive look into this must-have gemstone.
Origin & Composition of Tanzanite
Tanzanite originated from crystal which was formed millions of years ago – in fact it is a variety of the zoisite gemstone family.
The precious crystals grew in deposits on the inside of unusual elevations called inselbergs on a vast plain in the shadow of Mount Kilimanjaro. For centuries they were hidden from human eyes, until one day some passing African Masai shepherds noticed them sparkling in the sunlight.
Tanzanite is comprised of calcium aluminium silicate and is a blue variety of zoisite. Its value on the Mohs scale is between 6.5 and 7, meaning it is softer than many other gemstones and for this reason it should always be worn carefully and never brought into contact with acids.
History of Tanzanite in the Jewellery Industry
It was a Goan tailor and part-time gold prospector named Manuel de Souza who first introduced tanzanite to the western world. He found the vivid blue-purple gem crystal fragments in 1967 on a ridge of the Mererani Hills, some 40 km southeast of Arusha in Tanzania, Eastern Africa. Souza then showed the stones to a Nairobi-based consulting geologist and gemstone wholesaler with a Ph.D. from M.I.T named John Saul, who was mining aquamarine in the region around Mount Kenya. Saul then sent them to his father, Hyman Saul, who was Vice President at the famous Saks Fifth Avenue in New York. Hyman took the gems to the Gemological Institute of America, who correctly identified them as a variety of the mineral zoisite. Nevertheless, it was a man named Ian McCloud, a Tanzanian government geologist based in Dodoma, who was the first person to get the identification right.
Officially called “blue zoisite” at the time, it was Tiffany’s who, two years after its discovery, promoted the exclusive gemstone to the general public under the name Tanzanite, after its country of origin.
From 1967 to 1972, an estimated two million carats of tanzanite were extracted from the foothills of Mount Kilimanjaro before the mines were finally nationalised by the Tanzanian government. Currently, the mining of tanzanite nets the Tanzanian government approximately $20 million annually.
In Merelani today, the search continues for these coveted crystals in several, smallish mines. As a rule however, only small grains tend to be found, but every now and then the mineworkers succeed in discovering a larger crystal, which will sell for a fortune on the marketplace.
Preparing Tanzanite for Jewellery
Because tanzanite is relatively soft and delicate, it is most often set in necklaces and earrings.
Jewellers adore but fret over the sophisticated polychromaticity of tanzanite – its colour changes depending on the angle from which you look at it, so the gemstone may appear blue, purple or brownish-yellow at any given time.
Most raw crystals are somewhat spoiled by a brownish-yellow component, and this is made to disappear by the cutter heating the stone carefully in an oven to approximately 500°. During this procedure, careful attention must be paid to the moment at which the colour of the tanzanite turns blue.
Working with tanzanite can be a headache for cutting artisans, since it has a natural cleavage design that is pronounced in one direction. Care must also be taken for the gemstone to be free of inclusions as much as possible, since otherwise cracks can occur.
Grading of Tanqanite
The fact is there is no universally accepted method of grading coloured gemstones, other than the eye-clean standard which entails 20/20 vision to determine how many inclusions or flaws it has.
Nevertheless, TanzaniteOne, a major commercial player in the tanzanite market, has introduced its own colour-grading system for this unforgettable crystal which divides tanzanite colours into hues that range from blue violet to violet blue. In addition, the Gemological Institute of America classifies tanzanite as a Type I gemstone, meaning it is normally eye-flawless.
Because of its captivatingly outstanding beauty and the fact that it is only found in one place on earth, tanzanite will continue to be one of the most highly prized gemstones the world has ever known. The personification of immaculate taste yet unconventionally modern elegance, tanzanite jewellery is a must-have which cannot fail to make you stand out from the crowd.
About the Author: Julia Littlewood is a stylist and tanzanite enthusiast.