Sapphire is the gemstone form of a mineral known as corundum, with one important caveat: A sapphire is only a sapphire unless it is red, when it is known instead as a ruby. In fact there is one more stipulation to the rule, in the case of a pinkish-orange variety of corundum called padparadscha (derived from the Sinhalese word for lotus blossom).
Colours of Sapphire
Sapphires come in all manners of colours determined by the quantity of impurities present. Elements such as chromium, iron and titanium all contribute towards shifting the hue of the otherwise transparent mineral to a vast spectrum of colours such as yellow, pink, green, orange and the well known blue variety. Sapphires can also be found in tones of grey and black.
Properties of Sapphire
Sapphire is a very strong and hardy mineral, it not only has a melting point greater than 2000 degrees C but it is also infusible and insoluble. It is also an extremely hard mineral, at five times the strength of glass it is very resilient to scratching and as such has many practical applications other than for use in sapphire jewellery such as sapphire rings.
Practical Applications of Sapphire
Whilst sapphire is a highly sought after gemstone in the jewellery industry (having been used in items such as sapphire rings, bracelets, pendants etc.), uses have also been found for it in fields such as electronics and construction. The first laser ever made was with a rod of synthetic ruby – the red cousin of sapphire.
Sources of Sapphire
Sapphire comes in two varieties; natural and synthetic. Natural sapphire must be mined… naturally, and synthetic sapphire is grown through a procedure first developed by the French chemist Auguste Verneuil in 1902, later dubbed the Verneuil process.
Advancements in the production of synthesizing sapphire mean that today sapphire can be cheaply manufactured on a very large scale, making it all the more valuable for both industrial use and also in the jewellery trade.
The most significant source of natural sapphire is from Australia and Madagascar, although different varieties can be found in deposits all over the world.
A star sapphire is so named due to the appearance of a star-shaped pattern which presents itself when the sapphire is lit by a single top-down light source. This pattern is the result of a phenomenon known as an asterism. An asterism can be found in several types of gem, in star sapphires they are due to intersecting needle-like impurities.
Star sapphire jewellery valuation is dependent on the colour and intensity of the asterism present.
Natural sapphire jewellery is generally more expensive than synthetic sapphire jewellery as natural sapphires are obviously rarer, the problem however being that it can be extremely difficult to distinguish between natural and synthetic sapphires without help from an expert. The cost of the sapphire gems used in jewellery depends on several factors including colour, clarity, size, cut and quality.
As mentioned above, sapphire jewellery exists in a wide range of forms as with any precious gemstone. Highly popular are sapphire rings such as eternity rings and engagement rings.
The blue variety is perhaps the most valued form of sapphire on the market, and so often finding the highest price. Sapphires in the shade cornflower blue are the most prized and valuable, known as the ‘Kashmir Sapphire’ or ‘Cornflower Blue Sapphire’. The pinkish-orange corundum padparadscha however can fetch higher prices than even the finest blue sapphires.