LES PROPRIÉTÉS PHYSIQUES ET OPTIQUES DE LA TANZANITE
La Tanzanite est une variété bleue à violette de l’espèce Zoïsite, un minéral de la famille des Silicates. C’est un silicate de calcium et d’aluminium dont la formule est Ca2 Al3 (SiO4)3 OH. Sa teinte est due à la présence de vanadium. Son système cristallin est orthorhombique, sa dureté sur l’échelle de Mohs est entre 6 et 6,5. La tanzanite a un éclat vitreux, nacré, et sa densité est de 3,15 à 3,37. Sa fluorescence est nulle. Par contre, ce qui fait toute sa particularité tient à la force de son pléochroïsme, cette faculté à changer de couleur suivant l’orientation. Dans le cas de la tanzanite, il s’agit de trichroïsme : la pierre montre du bleu, du rouge-violet et de la couleur bronze selon l’angle d’observation.
LES COULEURS DE LA TANZANITE
La tanzanite est appréciée pour sa couleur bleue à reflets changeants. Cependant, elle existe aussi dans les tons de vert, jaune, rose, orange… Certaines, appelées tanzanites fancy, sont multicolores. La plus prestigieuse et la plus magnifique des tanzanites à plusieurs couleurs est la « caméléon » qui présente d’incroyables reflets. La majorité des tanzanites utilisées en joaillerie ont été chauffées pour intensifier leur couleur naturelle et atténuer les nuances brunes.
LES PRINCIPAUX GISEMENTS DE TANZANITE
La Zoïsite, pour être assez rare, est cependant présente dans de nombreux pays, comme l’Autriche, la Suisse, l’Italie, les Etats-Unis… En revanche, la Tanzanite, à part des quantités anecdotiques au Pakistan, n’a été découverte qu’en Tanzanie, et c’est toujours le seul endroit au monde où elle est exploitée. Les mines sont situées sur le territoire des Masaï, qui possèdent 95% du commerce de cette pierre. Mille fois plus rare que le diamant, et extraite dans des conditions de plus en plus pénibles des profondeurs de la terre où la chaleur est à peine supportable, le prix de la tanzanite est de plus en plus élevé car la demande est bien supérieure à l’offre. La zone concernée ne faisant que 20 km2, les gisements seront certainement épuisés dans un avenir assez proche…
COMMENT BIEN CHOISIR SA TANZANITE ?
Tiffany & Co a été la première entreprise à considérer la tanzanite comme une pierre précieuse de grande valeur et à la baptiser. Depuis, elle s’est affirmée chez de nombreux joailliers comme une gemme ouvrant de fabuleuses possibilités de création. Sa taille demande beaucoup de soin, car son clivage (faculté d’un minéral à se fracturer suivant une surface plane, conditionnée par l’agencement cristallin) est parfait mais dans une unique direction. De plus, du fait de son trichroïsme, l’orientation choisie pour la table, partie plane de la gemme, déterminera la couleur dominante (bleu, violet ou un peu des deux).
Les tanzanites sont la plupart du temps très pures, sans inclusions visibles, même au microscope. Les couleurs les plus prisées vont de l’outremer aux nuances de saphir. Plus les gemmes sont petites, plus elles tirent vers les tons lavande.
HISTOIRES ET LÉGENDES AUTOUR DE LA TANZANITE
La tanzanite a ceci d’extraodinaire qu’elle a été découverte très tardivement : elle était totalement inconnue jusqu’aux années 1960 ! La légende de leur apparition varie selon les versions, mais en somme, de violents orages auraient allumé des feux de brousse sur les collines de Merelani, non loin du célèbre volcan éteint, le Kilimanjaro. Les bergers qui s’étaient enfuis loin du sinistre finirent par revenir : c’est alors qu’ils découvrirent les cailloux bleus, à l’origine gris-bruns, transformés par la chaleur en superbes gemmes bleues… Il faut savoir que le bleu revêt un caractère sacré chez les Masaï. Elle est symbole de bonheur et de prospérité. Les bergers qui trouvèrent les premières tanzanites montrèrent les mystérieuses pierres à un explorateur, qui les envoya pour identification à un gemmologue. Celui-ci, perplexe, les fit parvenir à New York. Le GIA, (le Gemmological Institute of America), une autorité en matière de minéralogie, dut admettre qu’il s’agissait d’une variété jusqu’alors inconnue de zoïsite. En réalité, elle s’est formée par métamorphisme ou dans les pegmatites il y a des millions d’années, et à l’état brut, elle se présente dans des veines de gneiss, sous forme de prisme strié, avec des facettes.
VERTUS ET BIENFAITS DE LA TANZANITE
Malgré son apparition récente dans le monde étincelant des gemmes, les lithothérapeutes ont déjà trouvé de nombreuses vertus à ce minéral aux couleurs chatoyantes.
La tanzanite aurait des effets bénéfiques sur le cerveau et le système nerveux. Elle améliorerait l’ouïe et la vue, et faciliterait le travail du rein. Elle apaiserait les douleurs abdominales et gastriques et serait protectrice de la peau et des os.
La tanzanite stimulerait l’imagination et la créativité, elle serait en cela l’alliée des artistes, écrivains, musiciens et autres créateurs. Elle accroîtrait les capacités de mémorisation et la curiosité intellectuelle. Elle élèverait l’âme en quête de nobles aspirations, de recherche spirituelle toujours plus profonde. Elle faciliterait la bonne conduite de la méditation.
La variation « œil de chat » de la tanzanite apporterait intuition et clairvoyance.
Tout cela l’associe aux chakras supérieurs, qui sont situés au niveau de la gorge, des yeux et du sommet de la tête.
CORRESPONDANCES ASTROLOGIQUES DE LA TANZANITE
La tanzanite est associée aux signes astrologiques du Verseau, des Gémeaux, du Bélier, des Poissons et surtout du Capricorne. Elle symbolise les forces unificatrices. La tanzanite est la pierre de naissance des enfants du mois de décembre. Comme le satin, elle est le symbole du 24e anniversaire de mariage.
The Meaning and History of Tanzanite
Tanzanite is a member of the mineral family zoisite, which has been known about for nearly two centuries. Zoisite occurs in a number of varieties, the most sought after being tanzanite. This mineral family was named zoisite in 1805, some time after the Austrian scientist Baron Siegmund Zois von Edelstein (1747-1819) had identified the mineral in the Saualpe Mountains of Carintha, Austria. Siegmund Zois von Edelstein operated an iron mine in the Karawanken Mountains in Karnten Austria and encountered the mineral on his own property. Centuries later, the discovery of a bright blue transparent variety that we now know as tanzanite, created a lot of excitement in the specialist world.
A prospector named Manuel d’Souza who was looking for sapphire discovered tanzanite in 1967 in northeastern Tanzania. D’Souza was originally from India and had been looking for stones in the wilds of Tanzania. Eventually, some natives took him to an area in the region of the Merelani Hills near Mount Kilimanjaro, around 90 kilometers from his home town of Arusha. There, he found these precious blue stones he thought were sapphire. According to legend, the Masai herders were actually the ones who originally discovered the stone, when a lightning strike set the surrounding grasslands on fire. When they returned to the land with their livestock, the blue stones were all over the ground. D’Souza soon discovered that the blue stones he had found were not sapphire, so he staked a claim with the government and began mining.
With few inclusions, by 1970, the royal blue find was soon the focus of American and European publicity. When word of the new gemstones got out, Henry Platt of
Tiffany and Co. named the new gem “tanzanite” and Tiffany’s began a marketing campaign to introduce it to the public. Now, tanzanite is the pride of the
gem-rich East African country, Tanzania. Soon after word of this new precious stone got out however, a murderous attack put a swift end to exploitation of the mineral. A fake car accident, in which d’Souza died, interrupted any follow up supplies. As a result, supply was unable to keep up with demand during the following two years.
Some say D’Souza’s discovery is one of the most exciting in the field of gemstones in nearly a century. Of all the new gemstones that have conquered the hearts of people in the second half of the twentieth century, none has even approximated the success of tanzanite. Within a short period of time it has succeeded in achieving worldwide popularity and major acclaim. The triggering factors for this market success are the virtues incorporated in tanzanite such as the beauty of its color, its rarity and durability, as well as its availability. Though it only rates a 6.5 on the hardness scale, its resistance to scratching and abrasion is relatively good.
Tanzanite has become one of the most popular gems in the market place. In fact, it is now the most popular gemstone after the “big four,” which consists of diamonds, rubies, sapphires and emeralds. At first, the gemstone was only available in smaller sizes, but now much bigger sizes are sold. Today, tanzanite can cost over $2000 per carat in larger sizes at retail stores. Tanzanite is far less expensive than sapphire, for which it often serves as a substitute.
Tanzanite stones are 585 million years old. There are apparently only very rare tanzanite stones that are naturally blue. Given its attractive color, rarity and the publicity, which greeted its discovery, the value of tanzanite is quite high, just a little less than that of the violet-blue
sapphires
it resembles. But it is rarely seen on the market and is very much a collector’s item.
Tiffany's has one of the largest and most beautiful displays of tanzanite in the world.
The Smithsonian
Institution also has an impressive collection consisting of one faceted stone of 122.7 carats and a rare
cat's eye
tanzanite of 18.2 carats.
Because tanzanite was only first discovered in 1967, there is not much history, legend, or superstition about the gemstone. In Tanzania, however, women who have just given birth wear blue beads and fabric to bestow a healthy and positive life upon their newborns. This custom has been going on for generations in Tanzania.
Mystical Powers of Tanzanite
*The information provided here is for entertainment and reference purposes only. It is based on centuries of folklore, most of which camethe birthstones of your loved ones, or your favorite combination of colors about before the age of modern medicine. It is not meant as actual medical information. For advice about any of the illnesses listed, please visit a qualified physician.
Mentally, there are many ways in which tanzanite can be helpful to one’s life. It has the power to transform negative energies into positive ones. It assists in manifesting your own self rather than being influenced by others or trying to conform to the norm
Tanzanite changes colors when it is viewed from different directions. This shifting of colors has been said to facilitate raising consciousness. It aids in realizing your own ideas and transforms destructive urges into constructive ones. The gemstone opens an awareness of the comparison between how one lives and how one could choose to live more consciously. Those who wear it will become aware of their calling. It is a stone for highly developed beings who have not yet recognized their strength and fearfully close their hearts to it. This creates trust and we gradually open ourselves for further possibilities. On the level of sub consciousness, it helps us to better come to terms with ourselves.
Tanzanite dispels lethargy and brings repressed feelings to the surface so that they can be expressed. Tanzanite is a creative stone, bringing us back to our objectives after interruption. It also has the power to dissolve old patterns and creates space for new patterns to be integrated.
Physically, tanzanite is a wonderful tool to encourage recovery from severe illness or stress. It strengthens the immune system, regenerates cells, and treats the heart, spleen, pancreas, lungs, head, throat, and chest. The stone is also a great detoxifier. It also has the ability to neutralize over acidification and reduce inflammation. Tanzanite also stimulates fertility and heals diseases of the ovaries and testicles. It has been said that it is extremely beneficial to wear or place the tanzanite on the body in direct contact with the skin, where appropriate. It is recommended to wear the tanzanite for long periods of time, as it is a slow acting stone.
Physical Properties and Science of Tanzanite
Tanzanite rates a 6.5 on the
hardness scale
and has vitreous
luster. It is a relatively soft and brittle stone, nowhere near as hard as a
sapphire or a
diamond, but given the proper care it can last a long time.
The typical color of tanzanite is blue with a violet tinge. In some lighter colored stones, the color is described as lavender. The color of the tanzanite is the most important factor in determining its price. For example, a tanzanite of the perfect blue brilliant hue in 5, 10 or 20 carats is of greater value than a paler, darker, or duller stone of twice the size and weight.
In nature, tanzanite only sometimes occurs as a blue stone, but more often is golden to brown in color. After some time, it was discovered that by heating the brown or golden variety of the stone to 600 degrees Celsius and gradually cooling it, the color could be permanently changed to the violet-blue color. Without heating, tanzanite would be unmarketable.
Tanzanite is pleochroic, meaning the purple, gray, blue and violet tones within the stone vary depending on the angle the stone is viewed from. There might also be a slight color change in incandescent light, when stones may appear to be more violet. Tanzanite’s color is caused by the amount of chromium present in the stone.
Tanzanite’s rich, royal velvety blue resembles the precious Kashmir sapphire. Only a hint of violet and a slightly less hard and lustreous appearance than sapphire, tip off experts that the stone is something else. While at one point in time, tanzanite was used as a less expensive alternative to sapphire; it is now appreciated far more for itself and far less as a sapphire substitute. Tanzanite is much softer and fragile than sapphire and can occasionally shatter. It is important therefore, if you are having your tanzanite repaired or cleaned, that you make it clear that it is a tanzanite stone so extra care may be taken.
Tanzanite is often round or oval cut. It is a stone that normally has few inclusions, but as in all gem stone families, large, clear, nearly flawless tanzanites are rare. The larger the stone, the greater the chance of flaws occurring.
Being little known and of very recent history, this stone has neither been imitated nor produced synthetically. Tanzanite’s fire factor, especially that of the splendid blue color, is comparatively high, for this reason the tanzanite alone of all the zoisite family can be classed with any other splendid gem. Tanzanite is a rare gem likely to gain in value as a collector’s item.
Tanzanite occurs in schists and gneisses as well as in metasomatic rocks together with
garnet,
vesuvianite
and actinolite. It is also occasionally found in hydrothermal veins. Tanzanite is found in very limited quantities, almost exclusively in the northern part of Tanzania, near the Merelani hills, where the chief deposit is almost exhausted by now. However small amounts of tanzanite has also been found in
Sweden, New Hampshire, Pakistan, South Africa, Kenya, Norway, Austria, and
Italy.
Caring for your Tanzanite Jewelry
Care must be taken when setting or handling a tanzanite. The stone is soft and brittle so it can crack if one is not careful. It is also important to avoid exposure to sudden temperature changes or heat. Tanzanite is also sensitive to pressure and has a low resistance to ultrasound so it should never be cleaned with the ultrasonic cleaners commonly used by jewelers. It can suffer irreparable damage. In general, tanzanite should be worn with care.
