Sapphires have endured as one of the stones of choice for royalty and the well to do for centuries, and they are becoming increasingly popular as the centre stone for engagement rings and jewellery. Sapphires are the non-red variety of the mineral corundum (red corundum being a ruby) and they are most common in their blue form, although they can be found in a wide range of colours.
Besides blue, these include pink, yellow, green, orange, brown and clear. Sapphire is the name given to a couple’s 45th wedding anniversary (the 40th belonging to her sister stone, the ruby) and it is the birthstone of the month of September.
Colour is the most important determiner of value with coloured gemstones, including sapphires. The most desirable sapphires are known as “royal blue,” followed by “cornflower blue,” which take their name from the fact that the cornflower is almost unique among flowers because its petals are pure blue.
Tone refers to how light or dark the colour within the stone is, ranging from very light to very dark. Once again, the darker the stone the rarer and hence more expensive it becomes. Saturation relates to the vibrancy of the colour, covering a full spectrum from dull to pure vivid (with the finest appearance of colour). High saturation, vivid stones without elements of brown or grey areas, referred to as extinction, fetch the highest premium. Unlike diamonds, sapphires and all other coloured gemstones do not have a fully standardised system, which can make comparison between stones more complicated.
The padparadscha Sapphire is a very rare pink-orange fancy sapphire from Sri Lanka and Myanmar (Burma) that can fetch over $25,000 USD per carat and it derides its name from the Sanskrit “padma raga,” meaning “lotus colour,” due to its resemblance to the lotus flower.
Truly flawless sapphires are almost non-existent and in fact a stone with no inclusions will instantly arouse suspicion that it might be synthetic or heavily treated. The vast majority of sapphires (some estimate over 90%) available today have been heat treated in some way shape or form. Due to the prevalence of inclusions in sapphires, it is “eye clean” stones that tend to be the more attainable, rather than “loupe clean.” As with rubies, some sapphires contain ‘asterisms.’ These are created where light is reflected from the silk to form a ‘star’ shape, adding value to the stone.
Unlike diamonds, there are no standardised cuts for sapphires so in essence it is down to the cutter to produce the best possible shape to maximise a sapphire’s colour and clarity. As a rule of thumb however, a well-polished sapphire will be symmetrical, and it will reflect and refract light in the optimum angles to give the stone the best possible account of itself. With very light stones it is sometimes necessary to cut very deeply to accentuate its colour. With very dark stones the opposite is true and shallower incisions can produce the best results. In general, the most desirable shapes are oval, round, cushion and emerald but a non-faceted cut, such as a cabochon, can often do justice to a sapphire containing an asterism or double asterism.
Gemstones differ widely in terms of their density; a fine emerald may be as much as 30% larger in terms of its dimensions versus a diamond. Sapphires are generally heavier than diamonds so a sapphire may appear slightly smaller than a diamond of the same carat. Consequently, it is sometimes more useful to measure a sapphire in terms of its diameter in millimetres rather than its carat; a 1 carat sapphire generally measures around 6 mm.
Sapphires have endured as one the key precious stones of choice for royalty and the well to do for many centuries but in more recent times they are becoming increasingly popular as the centre stone for engagement rings and bridal jewellery. As with all things luxury celebrity endorsement has helped this rising popularity, not least as a result of Prince William’s decision to propose to Katherine Middleton with an 18 carat blue sapphire that was once in the possession of his mother Diana, Princess of Wales.