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4th September 2008 14:19

Sapphires

 

As sapphires are the birthstone of September so you may be thinking of looking for a sapphire birthday gift for someone, I thought that some information on coloured sapphires might interest you.

Any gem quality stone within the corundum family is generally called sapphire unless it is red, when it is a ruby; or pink and orange, when it's a padparadscha. They share many of the same characteristics and are the hardest, most durable stones after diamonds. In fact, corundum is so hard it's often used in industry for abrasive and cutting purposes, like in emery paper and drills. Rubies and sapphires are also used in laser: in 1960 the very first laser was invented by a man named Maiman, and he used a ruby to create the laser beam. This may be why in Bond movies the laser that is going to slice our hero in half is red!

Sapphires are mostly found in Sri Lanka, formally Ceylon although they also come from Madagascar, Burma, Thailand and Tanzania amongst others.

Despite the fact that generally people think of sapphires as blue, there are a wide range of types and colours, but they also share the same refractive index, so can be identified easily by a gemologist. The blue stones are the most popular and sought after. If a sapphire is to be called blue it must not have more than 15% secondary colour tones within its structure. Any more than this and it becomes something along the lines of greenish-blue or violet which are then called fancy colours.

Although deep colour saturation within a sapphire is normally regarded as good because it gives a fine, deep colour (and therefore makes it more expensive) there is such a thing too much of a good thing. The blue colour comes from titanium and if there is too much of this in a stone it can look almost black which reduces its value as an overly dark effect is not generally desireable.

At the other end of the scale, clear, white sapphires are the purest form of corundum because they contain none of the trace elements which cause colouration. They are a good alternative to diamonds if you are looking for a clear stone because they are so tough. Having said that, large stones are not that widely available because it is not easy to find that purity in nature. Stones with colourless areas are more common and these are generally cut so that the colour is at the base. This means that when it is viewed from above the colour fills the stone

Pink sapphires have become more widely available since the 1990s when new deposits were found in Madagascar. Until then they were exceptionally rare and found only occassionally in Vietnam, Sri Lanka and Burma. Because of the new availability theien been treated with extrr popularity has increased. They can be found in a full range of the palest pink through to fuscia and all colours seem equally popular. The colour comes from traces of chromium

Orange sapphires are so rare rhat the ones we see have ofteem heat to achieve the vibrant colour.

Yellow sapphires also come in a wide range of colours and tones from light canary through to a deep golden yellow. Until the end of the century it was not known that sapphires were anything other than blue as so yellow sapphires were known as Oriental Topaz up to this point.

Green sapphires vary between light lime green and olive in colour. Many actually consist of very fine bands of blue and yellow which can be seen under a microscope, but blend if looked at with the naked eye and these were known as Oriental Peridot.

Lavender and violet colours of sapphires are quite rare and often reminiscent of tanzanite (although obviously more durable). They can be quite expensive in larger sizes if they are of a decent quality.

Star sapphires and rubies are classified a 'phenomenon' stone. They are likely to have contribulted to the legend and lore concerning the powers of the sapphire because the very first sapphires cut would have been shaped in a cabochon form and when the stars appeared no one could explain them.

We now know that star sapphires have to be cabochon cut to alow the six pointed star to be created within the sapphire, which happens because of the way a single point of light relects from the internal structure of the stone. This structure is made up of microscopic needles which cross at one hundred and twenty degrees. The correct angle of light entering the stone bounces off the needles and accentuates the appearance of the star.

Colour changing sapphires are also classified as a 'phenomenom' stone. Many people do not believe they exist until they see them in real life. Generally, in flourescent lighting these stones look blue and in incandescent light they look purple, although they also come in red/brown, green/red and green/yellowy green. The most exciting thing about these stones is that because of the colour change effect, a ring with one of these stones set in it can look like two different rings! A stone with a complete colour change is more expensive than a stone with a more subtle change.

Padparadscha is the only variety of corundum other than ruby that is not simply known as a colour sapphire. Its name is an ancient Sanskrit word which describes the colour of a lotus flower - pinky orange. Padparadscha is extremely rare and as such very expensive, particularly for a fine piece. Similarly coloured stones are not classified Parparadscha if they have any hint of reddish orange or brown in them, although these too are stunning stones

As well as the birthstone of September, sapphires are the astrological stone of Leo. The various colours are thought to protect he wearer from all sorts of evil, illness, stress and general harm, and as such, I think we should all wear them all the time!

 

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