For as long as people have treasured gemstones, rubies have been associated with power and emotion. They are the same colour as the blood that flows in our veins, and were always believed to hold the power of life. Its colour gave rise to a belief that an inextinguishable flame burned in the stone, and that this flame could not be hidden and would shine through any material wrapped around the stone.
Red is also the colour of desire, and rubies were thought to be able to remove evil thoughts, control amorous desires(!) and reconcile disputes.
Rubies are a gem called corundum, the same gemstone as sapphires. The conditions under which corundum forms has a great effect on its colour and appearance. Corundum is composed of aluminium and oxygen, and is naturally colourless. Trace amounts of chromium cause it to turn red, and the more chromium, the redder it becomes. This is why rubies vary greatly in saturation of colour. Chromium also causes fluorescence, which can add to the intensity of the ruby. The most valuable rubies are red or slightly purplish-red with vivid saturation (“Pigeon-blood”). Typically, these form in marble deposits, which makes them very hard to mine.
The most important historic source of rubies was Mogok in Myanmar (Burma). Mogok is about 90km north of Mandalay. These rubies have a vibrant red bodycolour, and glow a beautiful red. Today, the most important sources are Thailand, Myanmar, Cambodia, Sri Lanka and Vietnam. There are also deposits in Africa, though many are not yet being mined. Below is a superb Art Deco ruby and diamond ring, set with a 1.8 carat Burmese ruby in the centre.
Rubies have a hardness of 9 on the Moh’s hardness scale, making them second only to diamonds in terms of hardness.
Most rubies are heat treated to enhance their colour. This is permanent, detectable, and nothing to worry about. In fact, without heat-enhancing, there would be so few gem-grade rubies that they would be prohibitively expensive. The heating brings out the colour, and enlivens the stone.
Below is a before and after picture of the same ruby crystal showing the effect of heat-enhancing.
Wonderful rubies are often sold privately, and so it can be hard to get a glimpse of the top end of the market. However, at the auction of Elizabeth Taylor’s jewellery in December 2011 a superb 8 carat pigeon-blood ruby and diamond cluster ring (below) sold for a whopping 4.2million dollars!