Tanzanite owes much of its beauty to an unusual gemmological property called pleochroism, the ability to exhibit more that one colour. When viewed from different directions, tanzanite can look blue, violet, purple, bronze or even gray. This is because Tanzanite is a trichomic gem. Very few stones are trichomic and this is what makes tanzanite’s very easy to identify. Trichomic refers to three layers of colour. The more common layers are blues and purples but you may also see flashes of red, green, yellow, or even orange. The colour that gemmologists primarily speak of is the deep royal blue. Before a tanzanite is faceted, the gemstone cutter studies the crystal and decides which directional orientation will show the best colour. And typically, most cutters will try to produce a pure blue tanzanite. Unfortunately, cutting to achieve a blue colour sacrifices a lot of weight and results in a smaller and more costly gem. Yet the blue of the well cut tanzanite is so breathtaking that most agree the sacrifice is well worth it. Stones ranging over 4 carats and larger have been known to show the strongest blue colour. Smaller tanzanite’s are usually soft blue, light violet or lilac purple.
Tanzanite FactsTanzanite is a relative debutante to the world of gemstones with its discovery in the East African country of Tanzania in 1967, and has been heralded by many as the Stone of the 20th Century. Certainly its impact is undeniable, and in 2002 with its elevation to Birthstone for December in many ways crystallised this feeling into a reality. The legendary New York jewelers Tiffany & Co were the first to market the stone as a fine gemstone, in the rarefied echelons of Diamond, Emerald, Ruby and Sapphire, and gave the stone is name.
While Tanzanite is a relatively recent discovery, the gem is the cobalt ultramarine to sapphire blue example of a minerals that was discovered almost two hundred years ago, in the Austrian Alps.
Nearly all tanzanite has been heat treated to produce the striking violet-blue colour, with the natural colour being a rather dull and uninteresting yellow-brown.
With only one economic deposit currently in production Tanzanite is a member of the gemstone endangered species list. Estimates vary, but in all likelihood with consumption continuing at it current levels, the Merelani Hills deposits of Tanzania will be completely depleted within 20 year
Tanzanite while a beautiful stone has a low hardness compared to other gemstones, and should be worn with care in all but designs that prevent the gem from being knocked or scratched
Tanzanite – What Causes The ColourThe causal agent in the formation of Tanzanite’s colour is heating. When heated to 400-500 degrees C, the natural yellow and brown tints of the rough vanish and an amazing blue develops. The colour of the highest quality Tanzanite is described at Cobalt Ultramarine. Although a range of colours from ultramarine to a rich Sapphire blue are commonly seen. The most popular colour, and here availability seems to be the determining factor, is a strongly saturated blue, which shows a purplish almost Amethyst subordinate hue
Purchasing Tanzanite
The decision to purchase a Tanzanite is made for many reasons. Uppermost should be what will the resultant pierce of jewellery be. As has been mentioned Tanzanite exhibits a relatively low hardness (6.5-7 on Mohs scale) and having a perfect cleavage is not very resistant to knocks or scratching. Therefore it should be worn with care at all time and preferable in pierces such as earring, and pendant before the choice of an everyday ring is reached. With care a master craftsman can create a ring for daily wear that does justice to the gem and protects is within certain limitations of design.
ColourThe most popular colour is a saturated blue with a purple (violet) subordinate hue, often termed in the trade as “Blue Violet”, less desirable are stones with more purple (violet), which can reach a level where the stones are best described as “Violet Blue”. However that said beauty is in the eye of the beholder, and the final choice remands an intensely personal one.
LightingTanzanite is trichroic stone, that is to say it exhibits three different colours when viewed along each of the three major axis (x, y & z). This pleochroism from very strong violet blue to brown, means the stone appears different colours, when viewed from different angles. In daylight the appearance of the stone is more blue, while under artificial light a more Amethyst violet colour is seen in the same stone.
ClarityTanzanite is a transparent Type 1 gemstones as classified by the GIA (Gemological Institute of America), occurring most commonly as eye clean pieces. As such there is no reason to purchase an included piece unless a very large stone is required, than may exhibit minor inclusions.
CutThe stone is cut in all imaginable shapes from classical to modern. The brilliance of the stone can however be enhances with the addition of extra facets on the pavilions of the chosen cut
Cleaning Tanzanite Jewellery
When cleaning tanzanite at the Jewellery store, never allow the store to clean the stone in an ultrasonic machine, as it vibrates at high speeds, and the stone is very likely to crack in the process. Instead, it is best to clean tanzanite rings with warm soapy water and a soft cloth, or to take them for a professional clean and buff at your local jeweler’s.
The Care Of Tanzanite Rings
To keep a tanzanite engagement ring from becoming scratched or damaged with time, remove the ring before any type of activities which could expose your Jewellery to strong knocks or abrasions, such as heavy cleaning, gardening, exercise, etc.
Tanzanite Hardness
Most people are familiar with diamonds, which are extremely hard – however, tanzanite is a softer gemstone and should be handled with much more care than you would a diamond. Tanzanite is similar in hardness to an emerald, but is less brittle. It is ideally suited for wear in dress rings, earrings, and necklaces. As it is susceptible to damage from hard knocks, active people should consider tanzanite Jewellery that won’t be exposed to as many bumps, such as pendants or earrings. Similarly, additional protective mountings can be used to protect corners and girdle edges.Tanzanite rates 6.5 on the Mohs scale of hardness, which ranges from one to ten. For comparison, diamond is rated 10, and sapphire, 8.5.
What is “AAA” tanzanite ?
Unlike diamonds -no standard quality grading scales exist for tanzanite. As a result many companies have developed their own quality descriptions, like AAA, AA, A to denote the range of quality of their tanzanite. It is important for consumers to understand that this type of grading is descriptive rather than scientific – and as a result comparing “like for like” becomes a difficult process.
How durable is tanzanite?
Tanzanite has a similar hardness to an Emerald, but is less brittle. In order to preserve its beauty, simple precautions should be taken. It is ideally suited for wear in dress rings, earrings and necklaces. If you’re an active person, consider jewellery that won’t be exposed to as many bumps such as pendants or earrings. When cleaning tanzanite at the jewellery store, never allow them to clean the stone in an ultrasonic machine, which vibrates at high speeds – it its likely the stone will crack.
Is all tanzanite heated to turn blue ?
Zoisite forms reddish brown – and turns into blue when subjected to relatively low heat. However, this heating can occur naturally during tanzanite’s time in the ground, and some tanzanite does come out of ground already blue. The majority of tanzanite is gently heated after mining to remove the reddish brown colour.
What colour is the best?
Rich deep violet-blues and blue-violets are the rarest, and thus command a premium.Whether you choose a pastel or richer coloured tanzanite is down to your preference and budget, but please be aware that tanzanite’s colourful brilliance intensifies in larger sizes – you’re generally not going find deeper colours in smaller sizes. ie 2.00 carats.
There is no price difference between a violet (bV) or blue (vB) dominant tanzanite. Purple tanzanite (not to be confused with violet tanzanite ) trades at a discount.
