Color diamonds also known as fancy colored diamonds (or just fancy diamonds for short) are the rarest and most beautiful of all gemstones. Each piece is an original blend of characteristics. Natural colored diamonds are extremely rare which is why they are often astronomically expensive. To make these attractive fancy diamonds more affordable, the potential of colorless and lower quality fancy diamonds is exploited and their properties are enhanced in a laboratory. Diamonds which have undergone such enhancement are called “treated”.
The different colors of diamonds and their origins
Diamonds span the entire color range from colorless through all the colors of the spectrum all the way up to black. Some of the rarest natural fancy diamonds are blue, red and pink ones, which are also valued for their slight hint of other colors.
Each color variety has its own origin and unique characteristics and these are also influenced by laboratory treatment options. Some color shades are as a result of the presence of other chemical elements (boron and nitrogen in blue, nitrogen in champagne, yellow and orange, and hydrogen in gray) or other forms of carbon (graphite in the case of black diamonds), while others are due to physical phenomena (the pink color in diamonds is as a result of the crystal lattice becoming deformed due to high temperatures and pressure) or even the activity of some radioactive source (as with green diamonds).
What treatments do diamonds go through in a laboratory?
Once we know how the diamonds got their color, we can treat them in a targeted way. Of course, this is all done in a controlled manner in very well-equipped laboratories. There are several ways to enhance the color of a diamond:
Irradiation
A wide variety of colors such as yellow, orange, pink, brown, green, blue and black can be achieved by exposing diamonds to irradiation. After they are irradiated, the diamonds are annealed to get rid of any residual radiation. The exact conditions that the diamond is exposed to (the type of radiation, length of exposure, the annealing temperature) depend on the properties of the original diamond (e.g. whether the nitrogen atoms in the diamond’s structure are aggregated or isolated).
The disadvantage of this type of treatment is that the resulting color could change under certain conditions and this is because irradiated diamonds are sensitive to higher temperatures. They could be exposed to such temperatures for instance during soldering or even simple polishing when the piece of jewelry is created or repaired. It is therefore always a good idea to know what laboratory treatment the stone has undergone.
Annealing
The method of annealing involves exposing the diamond to higher temperatures and subsequent cooling in a targeted manner. If it follows on from irradiation, it produces yellow, orange and brown colors, and according to some sources, also purple, red and pink. Without prior irradiation, annealing produces blue, green, brown and ultimately yellow. The stone is simply annealed until the desired shade of color is achieved. Once again however, there is a risk that the color will change later if the diamond is exposed to high temperatures, for example during the jewelry making process.
The HPHT method
This type of laboratory treatment also works on the principle of changes in the internal structure of the gemstone. It simulates the extreme conditions under which diamonds are formed in nature, that is, high pressure and high temperature. The same equipment is used to treat diamonds as is used to produce lab-grown diamonds. A huge advantage of this method is that the result is considered permanent.
Using the HPHT method can improve the quality of colorless diamonds as it suppresses any unwanted brown tint. However, any brown coloration can also be worked with in reverse to turn an unattractive diamond into a desirable fancy version of yellow, greenish yellow or green. If the initial conditions within the diamond are favorable, it’s also possible to get blue, orange or pink colors. In some cases, the HPHT process is followed by irradiation and annealing to produce pink, red and purple colors.
Coating
The three treatments mentioned above are generally accepted in the jewelry industry, they don’t reduce the quality of the stone and gemological laboratories provide certification for diamonds treated in this way. Another way to influence the color of diamonds is through coating. However this method is no longer used today as it has fairly significant disadvantages.
This method does not change the properties of the gems at the atomic level. Coating is simply coating the stone with a layer of color to make the result appear fancy. A coating of a special silica substance is applied to cut and polished colorless diamonds as the final step. However the resulting color effect may not be permanent - stones treated in this way cannot be polished, the coating can get damaged quite easily, and the process reduces the chemical and heat resistance of the diamond.
How to shop with peace of mind
As the technology of treating gemstones improves, the laboratory testing done to determine the history of a given gemstone has increasingly become more and more difficult. Only in highly equipped gemstone certification laboratories is it possible to find out all the treatments a gemstone has undergone. All of this information is then entered into a certificate, which essentially acts as a kind of birth certificate for the stone.
If you want to make sure that the information you receive about your diamond at the time you buy it is accurate and the price is appropriate, pay extra attention to the diamond’s certification. We recommend that you only buy gemstones which have been certified by independent laboratories.
Treated fancy diamonds are a very good and also affordable compromise between purely natural colored diamonds and lab grown diamonds created in pre-prepared conditions. This is because you gain a natural stone that has undergone only minor treatment to enhance its natural beauty. A gemstone whose potential has been fulfilled.
