No gemstone is as symbolic of love as the ruby. A ruby is the ideal way to demonstrate love and passion. A perfect ruby is more valuable than any other gemstone.
On the Mohs Scale of Hardness the ruby is rated nine, just below the diamond, which registers ten. Like sapphires, rubies are a gemstone belonging to the mineral family corundum. The ruby’s unique red colour is due to the presence of chromium, so all other corundum gemstones are called sapphires.
Pigeon Blood Ruby Colour
When grading gemstones gemmologists refer to the Four Cs of Connoisseurship. In order of importance for rubies these are: Colour, Clarity, Cut and Carat. The most valuable rubies possess a deep red hue. The preferred shade is known as “Pigeon’s Blood Ruby” or “Burmese Ruby”, a dark red shade with a slightly blue tinge. It should be noted this description does not necessarily indicate a stone is from Burma; it is more likely to indicate the stone’s colour is comparable to that of a Burmese ruby.
Although Burma was once the world’s top ruby-producing country, today the mines rarely produce stones larger than a few carats. Rubies from neighbouring Vietnam offer a slightly purple hue. Those mined in Thailand display the desirable deep red colour with a brown hue. Called “Siamese”, this highly prized colour is considered only slightly less desirable than the “Burmese” colour. Rubies are also mined in Pakistan, Afghanistan, India and Nepal. The East African countries of Kenya and Tanzania have produced some stones with a strong red colour, but generally these rubies are of an average quality and size.
Clear and Transparent Ruby
Clarity is the second most important criteria for valuing rubies. Opaque stones are of little value, while a transparent ruby is highly prized. Slightly flawed rubies may be heat treated to improve clarity, although gemmologists may refer to a stone’s minor needle inclusions to distinguish a real ruby from a synthetic one.
Some rubies possess a shine known as “silk”, a feature caused by very fine needles of the mineral rutile. These deposits sometimes cause a star-shaped inclusion inside the stone. When held up to the light the stone will cause a beautiful display known as asterism. A cabochon cut displays the inclusion as a star, presenting an optical image which seems to glide across the surface when the stone is moved. Known as star rubies, these stones are rare, and the star should appear in the centre of the stone will its six rays completely visible.
Rubies were first synthesised in 1902, using the Verneuil Process. Today many of the rubies available on the gemstone market are synthetic, and known as Verneuil rubies. Only an expert gemmologist is able to tell the difference between a natural and a synthetic ruby. Garnets and tourmalines are similar to rubies, but neither stone is as hard as the ruby. The ruby spinel is identical in appearance to a genuine ruby.
When buying a ruby, choose a stone for its quality rather than its size. All the best rubies contain some inclusions, but are not usually visible to the naked eye. Colour is the most important valuable feature, so a dark red stone with more inclusions is more valuable than a lighter coloured stone with few inclusions. Cut is an important consideration. A good cut will make the ruby glow with a deep red fire. Ensure the stone is free of scratches and chips. Although a ruby is a tough, hard gemstone, it may chip or even fracture with rough handling.