As the centre for ruby trading, approximately 80 percent of the worlds rubies will go through Thailand. Not only is it the place to which serious ruby buyers flock but it also has the largest cutting factories and is renown for producing some of the finest examples of this brilliant red gemstone.
While Burmese rubies were once considered to be the best in the world, a preference in the United States for the darker, more intense deep red-coloured stones mined in Thailand has brought these sensational rubies to the fore. Their fiery, almost burgundy red hues are the colour of life and beautifully crafted into jewellery form the perfect physical representation of passion and love.
Rubies are composed of the mineral corundum, from which sapphires are also created, and is one of the hardest minerals on earth. In its’ purest state corundum is colourless but trace impurities such as chromium, iron and vanadium give it colour. Depending on the geographical location, the mineralogical composition will be different and it is this which gives rubies from around the world their distinctive and varying reds.
Specific to Thai rubies is a phenomenon known as ‘extinction’. This only happens occasionally and is where the rubies have an inclusion which gives it a black reflection and makes them look darker in colour than they actually are. Imperfections and impurities are common in rubies however, as are fissures and cracks, and unless they seriously impede the light reflecting capabilities and core strength of the stone, they are accepted as part of the ruby.
In fact certain needle-shaped inclusions made from rutile (titanium dioxide) and known as ‘silk’ can help gemologists to determine real rubies from synthetic substitutes. One particular feature known as ‘asterism’ is created when light is reflected off of the rutile and is highly desirable. It shows a 3 or 6 point star within the ruby which appears to glide across the stone as it moves.
It is because of these minor defects that most rubies will undergo some kind of treatment and it is not considered to negatively impact on their worth. These include heat treatment, to draw out impurities and heal fissures, and the filling in of cracks with special resins and oils which emulate the properties of the ruby. Rubies that do not need any improvements are few and far between and these tend to be considerably more expensive.
The treatment of rubies means that looking after them must be done with care. It is not advisable to use ultrasonic jewellery baths or harsh, abrasive cleaners. To keep rubies from Thailand looking at their best, simply soak in mild soapy water and gentle wipe with a soft cloth.