Natural color diamonds are valuable because the presence of color is an entirely natural process ensuring every stone is unique and one-of-a-kind. Diamonds exist that which have been subject to a one or number of treatments to enhance the color of the stone. In our experience, the presence of these treatments will significantly decrease the value of the stone and it would no longer be classified as a "Natural Color Diamond."
Whereas the Federal Trade Commission requires jewelers and members of the trade to disclose these treatments to consumers, unfortunately that is not always the case. For this reason, The NCDIA recommends that you purchase diamonds that have an independent laboratory report to assure that you know exactly what the origin of color is on your stone.
Common Known Types of Treatments
HPHT – The most widely known treatment for diamonds, combining high pressure and very high temperature. This treatment has been prevalent since a least the early 1950s. HPHT can make some brown and Type II diamonds more colorless, or can produce brownish yellow, orangy-yellow, green, blue, and even pink color. The color achieved through this process depends on the diamond selected for treatment. HPHT treatment is rarely detectable under a microscope and detection requires a qualified gemological laboratory. One of the first successes in detecting HPHT was the discovery by Bob Crowningshield of the GIA of the 595nm line, which along with other gemological properties, proved that the color had been treated. Laboratory reports would indicate "HPHT" as the "Treated" designation.
Irradiation - The process of irradiation entails bombarding diamonds with high-energy electron or neutron particles knocking carbon atoms out of place, physically altering the crystal lattice of the stone and causing a diamond’s color to change. Most commonly found colors in irradiated diamonds include green, blue, yellow and black diamonds. These diamonds will frequently exhibit an orange florescence and may have a higher concentration of color near the culet, the most likely place that a diamond is Irradiated in a lab. Irradiation treatment can usually be detected in a gemological lab with the use of a spectrophotometer. Lab report will show "Irradiated."
Surface Coating - A thin layer of a colored material is deposited on the diamond in order to change its original color. When the coated surface is viewed under high magnification, the presence of trapped air bubbles, or worn areas where the coating has been scratched off, may be apparent. This treatment could be difficult to detect if the coating was applied only to the girdle or pavilion region of the stone, which is frequently the case. The treatment is not permanent. Lab report will indicate "Coated".
Synthetic Diamonds - Synthetic diamonds (also known as laboratory-created diamonds and laboratory-grown diamonds) are produced in an artificial process, as opposed to natural diamonds, which are created by natural geological events. Synthetic diamonds frequently utilize HPHT or CVD crystal formation methods.
Detection and Independent Laboratory Reports
Qualified laboratories use sophisticated techniques to test your diamond for known treatments and issue reports of authenticity. In reviewing such a report for a natural color diamond, it is critical that the word "natural" be displayed as the origin of color. If a laboratory cannot determine the natural color, the words "undetermined" will appear on the grading report. If any laboratory report indicates the word “Treated” it means they detected HPHT or one of the treatments listed above.
A list of five expert quick tips to help make your natural color diamond purchase an educated as well as pleasant experience...