Ruby is a specie of corundum and ranges in color from orange-red to purple-red. It is medium light to very dark in tone and quite strong in saturation.
Chemical composition of a ruby is Al203 It is a hexagonal crystal that often comes in six-sided prisms, terminated by flat faces.
Ruby registers a 9 on the hardness scale and is quite tough, unlike the emerald, and not nearly as subject to breakage. Under long wave ultraviolet, a ruby will fluoresce red or orange-red to inert and under short wave should fluoresce moderate red to orange-red.
Rubies come from a number of areas including Burma, which is usually considered as the finest source of rubies in the world. The best Burma stones are medium dark and vivid red.
Thailand produces stones which are a bit dark in tone and range from purple to brownish red because they have a slight bit of iron in them. Africa (Kenya, Tanzania) produces stones that are normally highly included although reminiscent of Burma in color. Sri Lanka has occasional rubies but more often sapphires that often mask as rubies.
In the U.S.A., North Carolina and Montana produce a few stones. Australia produces fairly poor quality stones as does India and Colombia, Nepal and Pakistan.
Rubies tend to be valued partially by the country of their origin. Some rubies now come with authenticated certificates of origin and the word Burma will bring a characteristically premium price even when considered next to a Thai
ruby that may appear identical to the Burma ruby under incandescent light.
Under fluorescent light, the Burma ruby will appear to fluoresce slightly and take on a deeper saturation. This is a highly sought after quality. Burma rubies also have some fine rutile needles that are commonly referred to as “silk” that add rather than detract to the attractiveness of the stone and further establish it as a Burma stone.
In order to establish a country of origin, a certified lab such as the American Gemological Laboratories in New York, has to study the ruby for body color under various conditions, fluorescence and inclusions. If a ruby is certified
as a top Burma ruby, the price may be 1 1/2 or twice what it was as an unknown or as a presumed Thai ruby.
Rubies from Thailand tend to have a brownish or purplish overtone. Those from Sri Lanka are generally very pink in color and more correctly referred to as pink sapphire.
There are a number of ways to treat rubies to improve their color, clarity and ultimately, their value. The quick fix method is to dye or oil the ruby which will help hide fractures, inclusions and improve the color of the stone.
A further refinement of this is a diffusion process where stones are immersed in a chemical bath which contains a number of chemicals including chromium which gives the ruby its color in the first place. This color is carried in
the skin of the ruby by the chemicals and actually penetrates the skin. This generally produces a light tone and the tone is only a skin which will disappear upon repolishing.
The next common treatment is a heat treatment. Rubies stand heat far better
than emeralds do and it is fairly Gommon to heat both rubies and sapphires which tends to improve the color by driving out bluish or brownish tints and will tend to dissolve the transparency, lessening the “silk” inclusions on heavily included stones.
These treatments all are dependent upon temperature, time and cooling rate, but they will bring about a permanent change in the stone leaving no chemicals or treatment to be removed.
In top ratings, rubies are rarer than diamonds but the actual supply of top stones may vary greatly because of political situations. Many stones reach the world markets because they have been smuggled out of places (especially
Burma) through Thailand and other friendlier countries. There is a fair amount of profit to be made in the smuggling of rubies.
Smaller, included or industrial strength stones, are cheaper than their diamond cousins because they are more easily available.
The rhodolite garnet often approaches ruby in color, although tends to be more purplish than the ruby and less saturated but still are sometimes sold as rubies.
Tourmaline also occurs in many color ranges including ruby red and is sometimes sold as ruby.
A new stone called red spinel has a remarkable resemblance to ruby and is not often seen on the market because it is generally sold as a ruby.
Rubies have been synthesized since the late 1 800′s. There are two primary methods of synthesizing rubies – the fusion method and the pulling method. In the 1950′s, several manufacturers began flux growing rubies which takes considerably longer than the other methods and produces a stone much closer to its natural version. Flux grown rubies tend to be extremely clear and transparent with an orange overtone.
Fusion stones tend to be strikingly flawless looking while the flux methods may actually produce a number of inclusions resembling silk.
One clue to synthetic rubies is the cut. Because the material is cheaper and waste is not as much a problem, machine cuts such as square or rectangular cuts are more prevalent.
