Ruby is a natural deep pink or blood-red coloured precious gemstone belonging to the Corondum family. Yet, there exist contradicting opinions on the elements constituting a ruby and a pink sapphire. Rubies get their red colour from the traces of chromium like a pink sapphire. However, unlike in a pink-sapphire, the levels of chromium are high in a ruby. The saturation level of the stone decides the category of corundum it belongs. While some Asian markets accept rubies with small traces of pink, that is not the case everywhere. In most places, there are separate colour categories for red and pink corundum.
Colour is the main factor to consider while evaluating a ruby. However, it is not easy to achieve objective colour determination for rubies. In ancient times, traders described colours of rubies with names like 'pomegranate', 'China rose', 'saffron', and 'pigeon's blood'. These terms are specific to regions and are not universally recognized. Objective system for evaluating rubies is a recent practice and takes into account the colour and transparency of the stone.
There is only a fine blurred line between the pink and red colours of a gemstone. The desired colour of a ruby is a vivid, medium-dark red to little purplish-red. The ideal saturation level is vivid or strong with a medium to medium-dark tone. Also, depending on the source of the stone, the colour and tone of ruby changes. For example, fine rubies from Myanmar have a slight purplish secondary colour. Whereas, rubies from Thailand exhibit a 'garnet red' due to their dark tone. Additionally, the value of a ruby increases if the stone can fluoresce as that attribute can intensify its colour. Also, rutile needles can reflect light and enhance the colour of the stone.
One method to determine the origin of ruby, and to prove that it is ruby is its unique ability to fluoresce. Rubies found in Burma, form inside marbles and have fluorescence features. Whereas, Cambodian and Thai rubies form in basaltic rocks (iron-rich rocks) and do not fluoresce.
Like sapphires, rubies do not undergo the same clarity expectations as diamonds. This is because natural sapphires and rubies are scarce, and cutters do not grade them at 10x magnification. Hence, their grading is on an eye-level view, and an 'eye-clean' ruby becomes a high clarity gem.
The most popular ruby sources in the world are Sri Lanka (Ceylon) and Myanmar (Burma). Other notable sources are Thailand, Vietnam, Afghanistan, Cambodia, Laos, India, Nepal, Tajikistan and the United States.
For centuries, Myanmar (Burma) has been a major source of high-quality rubies. The renowned Burmese rubies have the perfect combination of silk, colour and strong fluorescence.
There are two main locations in Myanmar where one can find remarkable ruby stones - Möng Hsu and Mogôk Valley. Although exact dates are unknown, legends believe that for about a thousand years, the Mogôk Valley has been a source for rubies. The Möng Hsu area is a recent discovery and started mining in the 1990s. However, since 2008, Burmese rubies are not imported into the United States as Congress passed an act banning their import. Hence, only the rubies imported before the act are present in the United States. Due to this, the prices of the existing Burmese rubies are high.
Throughout history, Sri Lanka has been particularly known for gemstone formations. This feature brings its name as the 'Island of Gems'. Sri Lankan rubies lighter in colour tones and contain pink secondary hues. This makes them more brilliant and clearer in appearance. Apart from that, Sri Lankan rubies are famous for their fluorescence, presence of silk and colour zoning.