Ruby

 

Which colour would you spontaneously associate with love and vivacity, passion and power? It's obvious, isn't it? Red. Red is the colour of love. It radiates warmth and a strong sense of vitality. And red is also the colour of the ruby, the king of the gemstones. In the fascinating world of gemstones, the ruby is the undisputed ruler.

For thousands of years, the ruby has been considered one of the most valuable gemstones on Earth. It has everything a precious stone should have: magnificent colour, excellent hardness and outstanding brilliance. In addition to that, it is an extremely rare gemstone, especially in its finer qualities.

  

 

For a long time India was regarded as the ruby's classical country of origin. In the major works of Indian literature, a rich store of knowledge about gemstones has been handed down over a period of more than two thousand years. The term 'corundum', which we use today, is derived from the Sanskrit word 'kuruvinda'. The Sanskrit word for ruby is 'ratnaraj', which means something like 'king of the gemstones'. And it was a royal welcome indeed which used to be prepared for it. Whenever a particularly beautiful ruby crystal was found, the ruler sent high dignitaries out to meet the precious gemstone and welcome it in appropriate style. Today, rubies still decorate the insignia of many royal households. But are they really all genuine rubies? Read on to find out more!

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Only a little bit of chrome ...

Ruby is the red variety of the mineral corundum, one of the hardest minerals on Earth, of which the sapphire is also a variety. Pure corundum is colourless. Slight traces of elements such as chrome, iron, titanium or vanadium are responsible for the colour. These gemstones have excellent hardness. On the Mohs scale their score of 9 is second only to that of the diamond. Only red corundum is entitled to be called ruby, all other colours being classified as sapphires. The close relationship between the ruby and the sapphire has only been known since the beginning of the 19th century. Up to that time, red garnets or spinels were also thought to be rubies. (That, indeed, is why the 'Black Ruby' and the 'Timur Ruby', two of the British Crown Jewels, were so named, when they are not actually rubies at all, but spinels.)

  

 

Ruby, this magnificent red variety from the multi-coloured corundum family, consists of aluminium oxide and chrome as well as very fine traces of other elements - depending on which deposit it was from. In really fine colours and good clarity, however, this gemstone occurs only very rarely in the world's mines. Somewhat paradoxically, it is actually the colouring element chrome which is responsible for this scarcity. True enough, millions of years ago, when the gemstones were being created deep inside the core of the Earth, chrome was the element which gave the ruby its wonderful colour. But at the same time it was also responsible for causing a multitude of fissures and cracks inside the crystals. Thus only very few ruby crystals were given the good conditions in which they could grow undisturbed to considerable sizes and crystallise to form perfect gemstones. For this reason, rubies of more than 3 carats in size are very rare. So it is no wonder that rubies with hardly any inclusions are so valuable that in good colours and larger sizes they achieve top prices at auctions, surpassing even those paid for diamonds in the same category.

  

 

Some rubies display a wonderful silky shine, the so-called 'silk' of the ruby. This phenomenon is caused by very fine needles of rutile. And now and then one of the rare star rubies is found. Here too, the mineral rutile is involved: having formed a star-shaped deposit within the ruby, it causes a captivating light effect known by the experts as asterism. If rubies of this kind are cut as half-dome shaped cabochons, the result is a six-spoked star which seems to glide magically across the surface of the stone when the latter is moved. Star rubies are precious rarities. Their value depends on the beauty and attractiveness of the colour and, though only to a lesser extent, on their transparency. Fine star rubies, however, should always display rays which are fully formed all the way to the imaginary horizontal line which runs through the middle of the stone, and the star itself should be situated right in the centre.

 

 

Ruby-red means passion

Red for ruby. Ruby-red. The most important thing about this precious stone is its colour. It was not for no reason that the name 'ruby' was derived from the Latin word 'rubens', meaning 'red'. The red of the ruby is incomparable: warm and fiery. Two magical elements are associated with the symbolism of this colour: fire and blood, implying warmth and life for mankind. So ruby-red is not just any old colour, no, it is absolutely undiluted, hot, passionate, powerful colour. Like no other gemstone, the ruby is the perfect way to express powerful feelings. Instead of symbolising a calm, controlled affection, a ring set with a precious ruby bears witness to that passionate, unbridled love that people can feel for each other.

  

 

Birthplaces of fine rubies

Which is the most beautiful ruby-red? Good question. The red of a ruby may involve very different nuances depending on its origin. The range of those nuances is quite wide, and could perhaps be compared to hotel categories, from luxury accommodation down to a plain inn or hostel. For example, if the gemstone experts refer to a 'Burmese ruby', they are talking about the top luxury category. However, it does not necessarily follow that the stone is of Burmese origin. It is basically an indication of the fact that the colour of the ruby in question is that typically shown by stones from the famous deposits in Burma (now Myanmar): a rich, full red with a slightly bluish hue. The colour is sometimes referred to as 'pigeon-blood-red', but the term 'Burmese colour' is a more fitting description. A connoisseur will immediately associate this colour with the legendary 'Mogok Stone Tract' and the gemstone centre of Mogok in the North of Myanmar. Here, the country's famous ruby deposits lie in a mountain valley surrounded by high peaks. Painstakingly, gemstones of an irresistible luminosity are brought to light in the 'valley of the rubies'. Unfortunately, really fine qualities are quite rare even here. The colour of a Burmese ruby is regarded as exceptionally vivid. It is said to display its unique brilliance in any light, be it natural or artificial.

  

 

The journey to the world's most important ruby deposits takes us further on to the small town of Mong Hsu in the North-East of Myanmar, where the most important ruby deposits of the nineties lie. Originally, it was believed that these rubies would hardly prove suitable for use in jewellery, since untreated Mong Hsu ruby crystals actually display two colours: a purple to black core and a bright red periphery. Only when it had been discovered that the dark core could be turned into deep red by means of heat treatment did rubies from Mong Hsu begin to find their way on to the jewellery market. Today, the Mong Hsu gemstone mines are still among the most important ruby suppliers. In the main, they offer heat-treated rubies in commercial qualities and sizes between 0.5 and 3 carats.

  

 

Ruby deposits also exist in neighbouring Vietnam, near the Chinese border. Rubies of Vietnamese origin generally display a slightly purplish hue. Rubies from Thailand, another classical supplier, however, often have a darker red which tends towards brown. This 'Siamese colour' - an elegantly muted deep red - is considered second in beauty only to the Burmese colour, and is especially popular in the USA. Ceylon rubies, which have now become very rare, are mainly light red, like ripe raspberries.

Other ruby deposits are located in Northern Pakistan in the Hunza Valley, Kashmir, Tadzhikistan, Laos, Nepal, and Afghanistan. But rubies are also produced in India, where deposits with relatively large crystals were discovered in the federal states of Mysore and Orissa. These crystals have many inclusions, but they are, nevertheless, eminently suited to being cut as beads or cabochons.

Lately, people have begun to talk about East Africa as a source of rubies. Straight after their discovery in the 1960s, rubies from Kenya and Tanzania surprised the experts by their beautiful, strong colour, which may vary from light to dark red. But in the African mines too, fine and clear rubies of good colour, purity and size are very rare. Usually the qualities mined are of a merely average quality.

   

Colour above (almost) everything

As we have said, colour is a ruby's most important feature. Its transparency is only of secondary importance. So inclusions do not impair the quality of a ruby unless they decrease the transparency of the stone or are located right in the centre of its table. On the contrary: inclusions within a ruby could be said to be its 'fingerprint', a statement of its individuality and, at the same time, proof of its genuineness and natural origin. The cut is essential: only a perfect cut will underline the beauty of this valuable and precious stone in a way befitting the 'king of the gemstones'. However, a really perfect ruby is as rare as perfect love. If you do come across it, it will cost a small fortune. But when you have found 'your' ruby, don't hesitate: hang on to it!

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The ruby is a pink to blood-red colored gemstone, a variety of the mineral corundum (aluminium oxide). The red color is caused mainly by the presence of the element chromium. Its name comes from ruber, Latin for red. Other varieties of gem-quality corundum are called sapphires. The ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond.

Prices of rubies are primarily determined by color. The brightest and most valuable "red" called pigeon blood-red, commands a huge premium over other rubies of similar quality. After color follows clarity: similar to diamonds, a clear stone will command a premium, but a ruby without any needle-like rutile inclusions may indicate that the stone has been treated. Cut and carat (weight) also determine the price. 

  

 

 Physical properties 

 Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness. Among the natural gems only moissanite and diamond are harder, with diamond having a Mohs hardness of 10.0 and moissonite falling somewhere in between corundum (ruby) and diamond in hardness. Ruby is α-alumina (the most stable form of Al2O3) in which a small fraction of the aluminum3+ ions are replaced by chromium3+ ions. Each Cr3+ is surrounded octahedrally by six O2- ions. This crystallographic arrangement strongly affects each Cr3+, resulting in light absorption in the yellow-green region of the spectrum and thus in the red color of the gem. When yellow-green light is absorbed by Cr3+, it is re-emitted as red luminescence. This red emission adds to the red colour perceived by the subtraction of green and violet light from white light, and adds luster to the gem's appearance. When the optical arrangement is such that the emission is stimulated by 694-nanometer photons reflecting back and forth between two mirrors, the emission grows strongly in intensity. This effect was used by Theodore Maiman in 1960 to make the first successful laser, based on ruby.

  

 

All natural rubies have imperfections in them, including color impurities and inclusions of rutile needles known as "silk". Gemologists use these needle inclusions found in natural rubies to distinguish them from synthetics, simulants, or substitutes. Usually the rough stone is heated before cutting. Almost all rubies today are treated in some form, with heat treatment being the most common practice. However, rubies that are completely untreated but still of excellent quality command a large premium.

Some rubies show a 3-point or 6-point asterism or "star". These rubies are cut into cabochons to display the effect properly. Asterisms are best visible with a single-light source, and move across the stone as the light moves or the stone is rotated. Such effects occur when light is reflected off the "silk" (the structurally oriented rutile needle inclusions) in a certain way. This is one example where inclusions increase the value of a gemstone. Furthermore, rubies can show color changes — though this occurs very rarely — as well as chatoyancy or the "cat's eye" effect.

 

Natural occurrence  

The Mogok Valley in Upper Myanmar (Burma) was for centuries the world's main source for rubies. That region has produced some of the finest rubies ever mined, but in recent years very few good rubies have been found there. The very best color in Myanmar rubies is sometimes described as "pigeon's blood." In central Myanmar, the area of Mong Hsu began producing rubies during the 1990s and rapidly became the world's main ruby mining area. The most recently found ruby deposit in Myanmar is in Namya (Namyazeik) located in the northern state of Kachin.

 

Rubies have historically been mined in Thailand, the Pailin and Samlout District of Cambodia, and in Afghanistan. Rubies have rarely been found in Sri Lanka, where pink sapphires are more common. After the Second World War ruby deposits were found in Tanzania, Madagascar, Vietnam, Nepal, Tajikistan, and Pakistan. A few rubies have been found in the U.S. states of Montana, North Carolina, and South Carolina. More recently, large ruby deposits have been found under the receding ice shelf of Greenland. In 2002 rubies were found in the Waseges River area of Kenya.

Spinel, another red gemstone, is sometimes found along with rubies in the same gem gravel or marble. Red spinel may be mistaken for ruby by those lacking experience with gems. However, the finest red spinels can have a value approaching that of the average ruby.  

 

Synthetic and imitation rubies   

In 1837 Gaudin made the first synthetic rubies by fusing potash alum at a high temperature with a little chromium as a pigment. In 1847 Ebelmen made white sapphire by fusing alumina in boric acid. In 1877 Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing BaF2 and Al2O3 with a little Chromium at red heat. In 1903 Verneuil announced he could produce synthetic rubies on a commercial scale using this flame fusion process. By 1910, Verneuil's laboratory had expanded into a 30 furnace production facility, with annual gemstone production having reached 1,000 kg (2,205 lb) in 1907.

  

Other processes in which synthetic rubies can be produced are through the Czochralski's Pulling process, flux process, and the hydrothermal process. Most synthetic rubies originate from flame fusion, due to the low costs involved. Synthetic rubies may have no imperfections visible to the naked eye but magnification may reveal curves, striae and gas bubbles. The fewer the number and the less obvious the imperfections, the more valuable the ruby is; unless there are no imperfections (i.e., a "perfect" ruby), in which case it will be suspected of being artificial. Dopants are added to some manufactured rubies so they can be identified as synthetic, but most need gemmological testing to determine their origin.

  

Synthetic rubies have technological uses as well as gemological ones. Rods of synthetic ruby are used to make ruby lasers and masers. The first working laser was made by Theodore H. Maiman in 1960 at Hughes Research Laboratories in Malibu, California, beating several research teams including those of Charles H. Townes at Columbia University, Arthur Schawlow at Bell Labs, and Gould at a company called TRG (Technical Research Group). Maiman used a solid-state light-pumped synthetic ruby to produce red laser light at a wavelength of 694 nanometers (nm). Ruby lasers are still in use. Rubies can also be used in applications where high hardness is required such as material for scanning probe tips in a coordinate measuring machine.

  

Imitation rubies are also marketed. Red spinels, red garnets, and colored glass have been falsely claimed to be rubies. Imitations go back to Roman times and already in the 17th century techniques were developed to color foil red—by burning scarlet wool in the bottom part of the furnace—which was then placed under the imitation stone. Trade terms such as balas ruby for red spinel and rubellite for red tourmaline can mislead unsuspecting buyers. Such terms are therefore discouraged from use by many gemological associations such as the Laboratory Manual Harmonisation Committee (LMHC).   

From Wikipedia, the free encyclopedia