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September Birthstone - Sapphire Featured

The term sapphire is applied to all types of the mineral corundum (an aluminium oxide) except the ruby, Sapphires are much more common than rubies, and stones exceeding 10ct are not rare. Deposits are found in Kashmir, Burma, Thailand, Sri Lanka, Australia and Montana...

Colour

It is a popular belief that sapphires are always blue, but this is not the case. Sapphires come in a whole variety of colours and hues from deep blue to yellow, green, brown, pink and purple and to the very rare orange-pink sapphire, known as the Padparadschah. Non-blue sapphires are called "fancy-coloured".

The colour in violet stones derives from vanadium; in yellow and green stones from iron; and in pink stones from chromium. If no colouring pigment is present, the stones are known as "white" or "colourless" sapphires. The finest stones, however, are a deep velvety blue and used to come from Kashmir in India. Kashmir sapphires usually have a slightly milky lustre which is even more apparent in the sunlight.

Although they lack the brilliance of Sri Lankan sapphires, the Kashmir stone's unusual cornflower blue touched with sea green is prized by collectors. The colour of Kashmir sapphires, unlike other varieties, tends to keep its character in artificial light, which is one of the reasons it has always been favoured - jewellery usually being worn at night. Other types of sapphire can appear to change dramatically in different levels of light. It is important to remember, however that though the best sapphires came from Kashmir, not all sapphires of Kashmiri origin are of good quality.

Burmese sapphires are the next most valuable, and are much  less rare than the Indian stones. The colour tends to be darker and stronger, though they also have some of the desirable velvety quality.

Sri Lankan sapphire are the most common type of stone, and it is in Sri Lanka that most of the fancy-coloured stones originate. Blue Sri Lankan sapphires tend to be clearer and brighter than the Indian or Burmese varieties.

Sapphires from Australia are an almost inky blue-black with a greenish tinge when held up to the light. These are relatively inexpensive and even stones of 20ct are affordable. For this reason they are popular for use in modern, mid-priced jewellery. The very darkest Australian stones are of low value. Natural sapphires display a characteristic colour zoning, where colour appears to be concentrated in parallel bands. When sapphires are viewed through a loupe, this should be apparent, although the finest stones should have as little obvious banding as possible.

Clarity

In Burmese and Sri Lankan sapphires the inclusions (internal flaws) are often distinctive and are referred to as "silk" due to their lustrous appearance. This silk is normally made up of"white needle-like inclusions criss-crossing each other. In Sri Lankan Stones the needles are long while in Burmese stones the needles tend to be shorter and run perpendicular to each other. These flaws confirm that the stone is natural.

 

Cut

Gem-cutters try to produce stones with the best colour and clarity without sacrificing weight. For this reason, most stones cut straight from the mine in the countries of origin are asymmetrically shaped and do not have uniform facets. Native-Cut stones are quite common, even in important European or American jewellery, because for the jewellers to recur them would mean a loss of weight. European or American-cut sapphires are usually "mixed-cut".

 

Stones often confused with sapphires:

Tanzanite, a blue stone discovered in Tanzania in 1967, was first used in jewellery by Tiffany. Although this stone somewhat resembles sapphire, its steely purplish tinge and common flawlessness are distinctive. Tanzanite, most like the pale Sri Lankan sapphire, does not display the colour zoning characteristic of sapphires.

Spinel is another stone which can resemble both blue and fancy-coloured sapphires, as it is also found in a great variety of colours, however, have a higher dispersion (more brilliant fire) and greater clarity than sapphires.<p>

 

 

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