With the holidays just around the corner, diamonds are very trendy. But it can be difficult for buyers as well as sellers to appreciate the quality of a diamond. In addition, they must consider the existence of treatments and imitations.


The value of a diamond is determined according to the 4Cs rule: Carat, Clarity, Color and Cut. This facetted diamond classification used by the greatest laboratories was implemented by the Gemological Institute of America (GIA) in 1953. It the method used to produce quality reports on diamonds.

the metric carat is the internationally accepted weight unit. The word “carat” comes from the carob tree, whose seeds weighted more or less 0.20 grams and which was used in ancient civilizations as a measuring unit. Obviously, the higher the carat, the higher the price of the diamond.

The purity of a diamond is always established with a 10x magnification, whether through a magnifying glass or a microscope. The magnifying glass gives the final diagnosis. The diamond is assigned a degree if purity depending on the possibility to observe internal characteristics (inclusions) and external ones (surface imperfections that only affect the exterior of the stone) with a 10x magnification. There are several degrees of purity: Flawless (pure with a 10x magnification), Internally. Flawless (perfect internal purity), VVS1 and VVS2 (Very Very Slightly Included and Very Slightly Included), SI1 and SI1 (Slightly Included) and I1, I2, I3 (Included). An expert report, whether on classification or on classification and evaluation, usually includes a diagram of the diamond on which the main features of the stone appear.

Most achromatic diamonds (98%) contain nitrogen atoms that cause a very slight yellowy shade sometimes grey or brown. The diamond is worth more without any yellow, grey or brown shade. The “color” of an achromatic diamond is evaluated by comparing it to diamonds calibrated on a matte white background and with a corrected cold light source. When the system was implemented, the GIA decided to use letters D to Z – D being the most perfect achromatic, Z being light yellow. It is estimated that up to J, the yellow shade is only perceptible by trained naked eyes.

Quality of the size
The size will give the diamond its true beauty. Brilliance and fire of a diamond depend on its size. The evaluation of the quality of the size of a diamond depends on three great parameters: proportions, symmetry and polish. It is difficult for unexperienced people to classify the size; hence it is better to trust the great labs reports. Quality reports evaluate each of these parameters as follows: excellent, very good, good, fair and poor. According to the AGS (American Gem Society), very well cut diamonds can be worth up to 50% more than diamonds whose size quality is poor.

It is also important to make sure that the diamond has not been treated, which could diminish its value. The most common treatments are:
– Fracture fillings : for a long time, it exclusively concerned emeralds, but since 1987, diamonds can also be treated like some rubies have been more recently. The treatments are spotted with a microscope. There is a ash effect (or color reflection), or bubbles in the fllling material.
– Inclusion whitening: this treatment has been applied for longer than fracture lflling. It consists in laser drilling a thin tube in the diamond then injecting acids to whiten black inclusions and thus make them less visible. This treatment is easy to spot with a microscope and it is permanent.


Furthermore, it is important to raise consumer awareness regarding diamond imitations available on the markets such as natural achromatic stones like sapphire or zircon, for example; or lab-manufactured stones such as achromatic synthetic spinel. Nowadays, the most frequent imitations on the markets are CZ (dating from the 1980s) and a newbie called synthetic moissanite. Until the introduction of synthetic moissanite in the 1998, it was easy to recognize diamond imitations through thermal conductivity-based detectors; diamonds being way better conductors than imitations. It is no longer the case with synthetic moissanite. The safest way is microscope observation. However, just like before, some brands make special detectors meant to distinguish between diamonds, moissanites and CZs. It is important to check the detector’s reliability (i.e. having comparison stones) and to repeat the operation periodically.

In conclusion, if you wish to know the quality of a diamond and correctly determine its value, you had better ask for its certificate. It is thus easier for sellers to reassure clients on the quality of diamonds, and the latter will be able to buy diamond rings with confidence.

By Marie-Hélène CORBIN