Our last article was on what many see as a successor or direct challenge to Sapphire, Tanzanite, and this article will explain the basics of the formation of Sapphire and it’s rise in popularity. Sapphire is a variety of Corundum which appears blue, purple, yellow, green or pink. Red varities of Corundum are called rubies and are considered a entirely different gemstone, even though they are the same basic mineral (more on this in another article).
Natural Sapphires can be any of the colours mentioned above, although Sapphire is commonly associated with the deep blue colour, which is usually enchanced due to heat-treating up to 1800C which brights out a slightly deeper colour, much the same as Tanzanite. So widespread is the practice of heat-treating Sapphire that is considered very rare to have an untreated gem, and these are normally supplied with a certificate to certify there is no evidence of treatment.
The colour of Sapphire is measured by three seperate catergories which are Hue, Saturation and Tone. Hue is essentially a value that determines the similarity or difference between one colour and another, and is more simply understood as the basic colour of a Sapphire. Saturation is slightly more complex but is on a simple level, the level of brightness or colour within the basic colour. This can be easily seen on photographs were saturation is adjusted where low saturation will look grey or washed out with high saturation being very vivid and more warm. Tone is similar to contrast in that is measures the difference between two extremes. In this case it is the brightness and darkness of the colour that is evaluated.
Sapphire can also be made synthetically through a process known as the Verneuil process where fine powder is melted and then crystalized into Corundum gemstones such as Sapphires or Rubies. This is increasing useful because of Sapphire’s industrial uses in watches or as electrical insulators. Sapphire is also incredibly hard at 9 on the moh scale (diamond is the hardest at 10), which makes it useful for creating scientific equiptment.