Blue sapphire is a valuable primary colour gemstone of the Corondum mineral family. The value of the gemstone rises significantly with the purity of the primary hue. Blue sapphires get their alluring colour due to the traces of iron and titanium – which means the more the level of iron and titanium, the higher the saturation. Green, violet, and purple are the most common secondary hues in blue sapphires. Variations in these secondary hues determine the final look of the gemstone. A sapphire is ‘blue’ only when its secondary hues do not account for more than 15% of its colour. While purple and violet colours can enhance the beautiful bluish look of the stone, green colour can harm the overall appearance of the gem.
Sapphires are dichroic stones, which means that their colour differs according to the viewing angle. From one direction, a blue sapphire may appear violet-blue to blue while from another direction it may appear greenish-blue. It is the cutting of the stone that makes the difference in the finished look. A skilled cutter can align the stones while cutting and ensure that the most beloved blue colour appears through the finished stone.
The inclusion of grey in sapphire can create a steely or cool quality as opposed to the usual warm velvety colour and feel of a sapphire. This is commonly referred to as the grey mask as grey is the normal saturation modifier or mask in blue sapphires. Grey decreases the saturation or the brightness of the stone and therefore has an overall negative effect.
Blue sapphires devoid of inclusions or eye-clean are rare, particularly in large sizes. Yet blue sapphires with small internal inclusions are also valuable, considering the inclusions do not obscure colour, reduce brilliance, or diminish the stone’s elegance. The same holds for silk inclusions. Silk inclusions can even increase the value of blue sapphire. Heat treatment and diffusion are used to make appealing blue sapphires out of common corundum. Over 90 per cent of all blue sapphires in the market has been subject to heat treatment. Heat treatments used to modify clarity and colour of blue sapphires often break down rutile silk. Hence the presence of intact silk would mean that sapphire is not heated. There exist other liquid or solid inclusions that deform or burst under extreme heat and are therefore considered as indicators of untreated stones.
The cut of any sapphire is a crucial determining factor in its value and appeal. Depending on the quality and colour, a skilled cutter can cut a blue sapphire into various shapes with different cut styles. There are many factors like carat, stone brilliance, inclusions, and colour while deciding how to cut and shape a polished sapphire. Accurate and skilled cutting can bring out the sparkle and clarity of sapphire and ensure that it is an exquisite focal point for any piece of jewellery. Blue sapphires weighing one carat or more are not commonly cut to standard shape or calibrated sizes. Thus the weight and colour of the gem determine the shape of the stone.
Some of the most popular destinations in the world where one can find blue sapphires are Kashmir, Sri Lanka, Thailand, Myanmar, Australia, Madagascar, Tanzania, and Montana in the United States.