Sapphires are one of the world’s four precious gemstones which include emerald, diamonds and rubies. They are a type of corundum and its colours are determined by the concentration of certain elements such as iron, titanium of chromium.
Colour
Although Sapphires can come in many colours the most famous is red, which of course we call ruby. The value of a sapphire is largely determined by colour, clarity, cut and carat although where it was found is also an important indicator.
The major indicator of value in a blue sapphire is how true blue the sapphire is. Most sapphires have a secondary hue., usually shades of purple or green. The primary blue hue must be at least 85% blue for a sapphire to be considered good quality.
Pink sapphires are the most valuable shade other than blue. Pink sapphires become more valuable as they approach the colour of ruby, without actually becoming ruby. They have recently become more common on the market due to a new technique called lattice diffusion.
Shape
The most unusual sapphire is the star sapphire which causes an odd star like reflection called an asterism. The largest sapphire with this odd reflection is called the Black Star of Queensland which is 733 carats. There is also the Star of India which is the more traditional blue colour and weighs 563.4 carats.
Rare sapphires even change colour depending on the light. These sapphires may look blue in outdoor light and purple in artificial light. There are other types that may look pink outside and green inside.
Jewelery
Sapphire can be used in jewelery to make necklaces, bracelets, rings and earrings.
Like most gemstones sapphires are often treated to improve their clarity. This is usually heat treatment at up to 1700 degrees centigrade in air which will improve the colour, but also remove inclusions (trapped rock etc). You would think that would be a good thing but it shows that the gem is not 100% natural. 100% natural stones will often come with a certificate to prove so.
One of the oldest sapphires is the Stuart Sapphire which was mounted on Queen Victoria’s state crown. Even though it is slightly flawed it dates back to 1214 and can be seen in the Tower of London.
sapphire earrings
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