In Every Colour, At Every Price.

       If there were awards given to gemstones for their various attributes and qualities, then the top prize for versatility would surely go to tourmaline. Tourmaline occurs in every colour possible from colourless to black and every shade and hue in between. In fact, there are more than a hundred shades to choose from when one gets down to it. Sometimes a single stone will display more than one colour as in the case of bi-colour and tri-colour tourmalines.
       The most well known of these is the famous watermelon tourmaline, which has a pink centre and a green rind separated by a band of white just like in the fruit. Jewellery designers like to set slices of watermelon tourmaline instead of faceted gems as this shows off the colour combination to advantage. Another form of bi colour tourmaline shows a clear heart and a black border and is known as moor's head tourmaline.

       Actually, tourmaline is not just one mineral, it is a whole family of minerals related in physical and is a complex silicate of boron and aluminium. Many different elements are able to find a spot for substitution in the crystal lattice and this accounts for all the different colours of the gem. The exact species of tourmaline is determined by which of a number of possible elements is present in the specimen.
       The members of the tourmaline family include buergerite (brown), dravite (brown), elbaite (multicoloured to green), schorl iblack), and uvite (black, brown, yellow-green). The elbaite group can be broken down to include achroite, which is a rare colourless variety of tourmaline, rubellite (red), and tsilaisite (manganese rich).
  1 Bicoloured, doubly terminated tourmaline is representative of some of the fine-quality crystals of this gem.


2 The intense colour of fine-quality copperbearing tourmaline from the Mina da Batalha in Brazil.


3 Paraiba tourmaline.
   
       Tourmaline forms in a variety of geological settings. Mostly, it is found in granite pegmatites and in their immediate vicinity in the enclosing host rock. Pegmatitic tourmaline is commonly black and is associated with microcline, albite, quartz and muscovite. The light coloured gem tourmalines are much more rare, usually occuring in pegmatite core zones with quartz, clevelandite, muscovite, lepidolite and more rarely amblygonite and spodumene.

       Other areas of occurrence for tourmalines are with quartz in hydrothermal veins where heated mineral bearing liquids or gases from deep igneous sources later cooled and crystallised along rock fractures, in granites due to late stage alteration of micas and
feldspars by boron containing fluids, and by boron metasomatism in contact and regionally metamorphosed rocks. Because of tourmaline's relatively high hardness and specific gravity, it is often found in elluvial and alluvial deposits.

       As it is a pegmatite mineral, it is found in the world's great pegmatite districts. Foremost among these is the land of gems, Brazil. They are also found in California and Maine in the United States. Apart from the Americas, there is an abundance of the mineral in Africa as well, mainly in the East African nations of Kenya, Tanzania, Mozambique and Madagascar. Malawi produces some beautiful canary yellow material, while gorgeous rubellites and fine blue-green tourmalines can be sourced in Nigeria. Nor is Asia left behind as gem material can be found in Afghanistan, Pakistan, Burma and Sri Lanka as well.

       In fact, the name tourmaline has its roots in the Sinhalese language. It derives from the Sinhalese word turmali, which means many coloured gemstones. Bright rainbow coloured parcels of mixed gemstone varieties were called turmali by the Sri Lankan gem traders and tourmaline's ability to resemble almost any other gemstone, lives up to the derivation of its names.

      It is composed of long, prismatic crystals. Tourmaline crystals are often cracked and flawed, especially the reds, pinks and bi-colours, while the greens and blues are generally much cleaner.
     The most common inclusions in tourmaline are fractures and liquid filled healed fractures. Needle inclusions are also common. Sometimes in fact, tourmaline itself is found as needle like inclusions in other stones such as tourmalinated quartz.
     Tourmalines are often cut in long rectangular shapes because of their crystal shape. In fact, the crystal shape is often so beautiful, pencil thin and ridged, that sometimes designers choose to set it into jewellery in its rough state itself. As a matter of fact all tourmalines, regardless of their chemical composition, form similar crystals because they are isostructural meaning that they share the same internal crystalline structure.

     There is one particular iharacteristic of tourmaline that is of great advantage to gemstone alters. Tourmaline is a strongly pleochroic gem. The darkest colour is always seen looking down the ixis of the crystal. This feature allows gem cutters to play with the gem cutting darker stones in a way that will display the lighter of the two pleochroic colours or conversely, cut a lighter stone in a manner that displays the darker shade. If the gem is cut so that the c axis is oriented parallel to the table facet, then the stone will appear lighter in colour. If it is cut in a manner that orients the table perpendicular to the c axis, then it will display the richer colour in the stone.

     There are many other interesting characteristics to this gem. When faces are present on both ends of a natural crystal, they can be seen to have developed with different orientations and do not correspond. This phenomenon is known as hemimorphism, and it gives the stone certain electrical properties. Tourmaline is pyroelectric, which means that it develops a charge when it is heated. The Dutch traders noticed this and used long unfashioned crystals to draw ash from their meerschaum pipes and thus, they labelled this gem 'ashentrekker', which literally means ash puller.

     There is a downside to this magnetic quality though, as tourmaline, more than any other gem, attracts dust to itself while it is kept in display cases and thus needs to be cleaned more often than any other gem.
      Tourmaline also displays piezoelectricity when its crystal is placed under stress. Pressure will lead to the stone's charging and in the course of discharging, the plus and minus poles will alternate so that the stone will show vibrations like rock crystal, only it is much stronger in tourmaline. This property makes it very useful for application in underwater detection equipment, and depth and pressure guages. During World War II, it was much in demand for use in the production of pressure sensitive guages and submarine instruments as well as other war equipment. It has also been used as a calibration standard for the manometer and as a standard to check for the possible effects of water soluble boron used in mixed fertilisers.

     Another feature of tourmaline is that when slices of it are cut from a prism face along the length of the crystal, then they have the ability to polarise light.

      As mentioned earlier, tourmaline is a family of groups of minerals rather than a single one.
Burgerite is a rare species of the tourmaline family. It is usually easy to distinguish it from the othe more common tourmalines as it is brown and translucent to opaque However, it is easily confused wit another less common species dravite. Under normal circumstances it is difficult to distinguish between them as they both look alike. 111! main difference between the two is j that dravite is formed in metamorphic rocks and burgerite i formed in igneous rocks. Anothe: distinguishing factor is the present; of flourine in burgerite.

     Dravite" is a little know; species of tourmaline. Dravite wil sometimes produce large wel shaped crystals that are importai: speciments in rock collector' hoards.

      Dravite is brown in colon and is rarely transparent enough to be considered gem material. However, it can be heat treated to lighten the dark colour and is therefore sometimes cut into gems. Its crystals are typically elongated three sided prisms.
      Schorl is the most common mineral in the tourmaline family. It is black in colour. It can form the major component of metamorphic and igneous rocks and although it is not the only black mineral common ;o these rocks, it is the only one that will form crystals with a clear triangular cross section. In fact, long thin crystals of schorl are common as inclusions in quartz and they form the ornamental stone known as tourmalinated quartz. By and large though, schorl has no use as gem material.

      Uvite was earlier thought to be a rare form of tourmaline but it has now become fairly common in the mineral market. Uvite is the magnesium/iron rich member of the tourmaline family and has one notable exception to the typical tourmaline generalised formula, in which the 6 aluminium atoms are reduced to 5 and a magnesium atom is inserted into the missing aluminium's position.

      Another odd thing about uvite is that in spite of having so many colouring ions like iron and magnesium, most varieties of this species are actually quite colourless. Nevertheless, most specimens of uvite in the market are dark green to black in colour. Another feature that distinguishes uvite from the other tourmalines is its stubby crystals rather than the long prismatic crystals of the other species. Uvite crystals are still well formed though, and show all the interesting features that make tourmaline such a pleasure to collect.

      Elbaite crystals are recognisable by their prismatic form, typically elongated like pencils with cross sections that range between hexagonal and trigonal. Elbaite is also the most strongly pleochroic of the tourmaline family. It is the mineral responsible for almost all the gem varieties of tourmaline. Although elbaite is a separate group of minerals in the tourmaline family, in the gem trade this name is used to refer to green tourmaline only. All the other forms of elbaite have their own trade names.

     Green tourmaline is the most recognised of tourmaline colours. They are typically eye clean stones whose colour ranges from a pastel to a deep vibrant green.

      Chrome tourmaline is a rare variety of green tourmaline that is found only in Kenya, Zambia, Tanzania and Namibia. The finest chromes rival the top colour of emerald and offer a more durable stone for jewellery. The colour is due to the presence of chromium or vanadium. It was first mined in Tanzania in the early 1960's.

       Blue tourmaline is known as Indicolite and the finest colours of this stone are in the medium dark blue range, which is very close to the blue of the famed Kashmir sapphires. There are some which come in turquoise blue-green colours that are close to but not quite as vivid as paraiba tourmalines. Like green tourmaline, indicolite is also usually eye clean and inclusions are quite rare.

      The most famous and rare of all tourmalines is the paraiba nirmaline. It is one of the world's most unusual gemstones. It was discovered in Brazil in 1982 and at first it was called electric tourmaline and then subsequently neon tourmaline. However both these names lacked the cachet of paraiba (derived from the state of Paraiba in Brazil where it is found), which is the name that stuck.

      Paraiba has the most fascinating colour range of any gemstone yet - vivid turquoise, electric blues, neon green, rich twilight blues. It is the only variety of tourmaline that contains copper. A study conducted by the German Foundation for Gemstone Research found that paraiba tourmaline also contains significant amounts of gold, nearly 8.6 parts per million. When you take into account that the average gold content of the earth's crust is 0.007 parts per million, you can appreciate exactly how high the gold content in paraiba tourmaline is. In fact, if it were not such a beautiful, expensive (retail prices are said to go up to $20,000 per carat for the finest specimens) and rare gem, it would be crushed to salvage the gold.

      Like tanzanite, paraiba tourmaline is also found in only one location in the world, in a football field sized patch of land near the village of Sao Jose da Batalha in the state of Paraiba in northeastern Brazil. Production is sporadic and doesn't keep pace with market demand. The mine shafts are hand excavated tunnels upto 60 metres deep and the gem is found only in thin veins. Therefore, supply will always be strictly limited and the prices for this gem are not likely to ever decrease.
Yewllow, orange ana gold tourmaline

      In 2001, there appeared on the market beautiful bluish green tourmalines from Nigeria that were just a bit lighter than paraiba. Like paraiba, these too showed their best colour after being heated. Also there are no diagnostic features to separate them from paraiba. The similarity in the chemical components between the Nigerian and Paraiba stones can be explained by the presence of the copper mines in Nigeria.

Experts theorise that the presence of this unique gem in only two locations on two separate continents can be explained by the theory of continental drift. Continental drift is the seperation of one original super continent into the different continents we know today by the force of geological processes and if the coastlines of South America and Africa were put together they would fit each other just like the pieces of a jigsaw puzzle. Therefore, it is possible that the gemstone was created in both Brazil and Nigeria under similar conditions before the two continents drifted apart.

      Pink tourmaline is perhaps the most popular of the tourmalines for range all the way from the palest light pinks to hot pink, fuchsia, and orangy pink. Gemmologists feel that the pink, red and violet colours in tourmaline are produced by the process of natural irradiation, However, there are artificial enhancements that can do the same thing. Intense hot pinks can alsok attained by cobalt treatment. The darker reddish colours tend to be the most included type of tourmaline because they form near the centre of the crystal pocket and therefore they generally receive more stress and pressure during formation.

      Then there is rubellite tourmaline, which is named for the deepest reds that look like rubies. Eye clean rubellite is among the most expensive kinds of tourmaline because as mentioned earlier, the reds have a tendency to be heavily ,included. There is also a rubellite garnet which is generally clean material and is also at a fraction of the price of rubellite tourmaline.
Thefore if you find a rich ruby red gem which is also eye clean, chances are that it is rubellite garnet and not , rubellite tourmaline. The colours range from fuchsia to maroon red to red. The price goes up in direct proportion to the size, cleanliness and intensity of colour of the gem.
     
      Watermelon tourmaline is so called because it quite literally resembles a watermelon. It has a green rind followed by a white band and a red centre. Sometimes the inclusions in the red centre look like the seeds of the watermelon. As mentioned earlier, this kind of tourmaline is cut into slices to best show off the beauty of the gem. There are also other bi coloured and tri coloured tourmalines and the colours may separate either along the width or the length and will thus determine how the stone will be cut to best show off all the colours.

      There is also a rare alexandrite tourmaline which changes colour just like alexandrite. Its daylight colouring is yellowish/brown green which turns to red under evening light. Chatoyancy is seen in the cat's eye tourmaline and this is due to the crystals growing fluid filled tubes along the long, prismatic axis. These are usually cut as cabochons. There are also orange and yellow varieties of tourmaline that do not have any special name to distinguish them and are known by their colour like pink tourmaline is. Anchorite is a colourless variety of tourmaline. There is also an attractive purplish coloured tourmaline that is called siberite. This name applies only to the stones found in Russia's Ural Mountains.

     
      Almost each and every colour of tourmaline can be found in Brazil especially in the gemstone rich states of Minas Gerais and Bahia. Tourmaline is also mainly mined in Tanzania, Kenya, Madagascar, Mozambique, Namibia, Nigeria, Afghanistan, Pakistan, Sri Lanka, and in the states of California and Maine in the United States of America. Some gem tourmaline is also found in Burma.
       Although there is some historical evidence of tourmaline being used as an ornamental stone as far back as 27 B.C. to 395 A.D., there is not much folklore built up around it. It was discovered on the island of Elba early on and hence the name elbaite. The Dutch brought it from Sri Lanka to Europe in the 1600's and many stones in the Russian Crown Jewels from the 17th century that were once thought to be rubies are actually tourmalines.

      The Empress Dowager Tz'u Hsi, the last Empress of China, particularly loved pink tourmaline. She is reputed to have bought a ton of this material from the Himalaya Mine in California and she is said to be buried on a carved tourmaline pillow. The good news is that you do not have to be an empress to enjoy this beautiful gem. Apart from the diversity of colour, its availability also swings from easily available at a few dollars a carat to the rare can be had only for thousands of dollars a carat. Therefore there is a tourmaline to suit every taste, every pocket and allows for bragging rights along a very diverse economic spectrum.