DIAMOND

At this time of year when wedding rings and engagement rings are in high demand, diamonds are highly prized. However, it is sometimes difficult for both the consumer and the seller to determine the quality of a diamond, especially with the existence of synthetics and treatments.

The 4C

The value of a diamond is determined according to the 4 Cs: Carat, Clarity, Colour, and Cut. Developed by the Gemological Institute of America (GIA) in 1953, it is still the method used by major laboratories that issue diamond quality reports.

Carat (Weight)

The metric carat is the internationally accepted unit of weight. The word Carat comes from “carob” seeds used by ancient civilizations as a measure of weight. A carat is exactly 0.2 grams, therefore making 5 carats equal to 1 gram. Of course, the higher the carat, the higher the price of the diamond.

Clarity

Determining the clarity of a diamond, although microscope may be used, the final decision is decided with a 10x magnification loupe. Clarity grades are assigned based on how easy or difficult it is to observe the internal (inclusions) and external (surface imperfections that affect only the outside of the stone) characteristics of the stone. There are different degrees of clarity: FL (Flawless) – No inclusions or surface blemishes; IF (Internally Flawless) – No inclusions, minor surface blemishes which can be removed with repolishing; VVS1 and VVS2 (Very Very Slightly Included) – Minute inclusions difficult to detect; VS1 and VS2 (Very Slightly Included) – Tiny inclusions difficult to detect; SI1 and SI2 (Slightly Included) - Inclusions detected with magnification; and I1, I2, I3 (Included) – Inclusions detected without magnification. Generally, an appraisal report, either classification only or grading and appraisal, usually includes a diamond diagram showing the main characteristics of the stone.

Colour

Most colourless diamonds (98%) contain nitrogen atoms responsible for a very slight shade of yellow – or sometimes a shade of gray or brown. A diamond is all the more valuable if it is perfectly colourless without any shade of yellow, grey or brown. The "colour" of a colourless diamond is evaluated by comparison with calibrated diamonds, on a matte white background, and under a corrected cold light source. The intensity of the colour is observed rather than the colour itself, as some diamonds will have a slight shade of gray or brown rather than yellow. When developing the system, GIA decided to use the letters D to Z, D being the most perfect colourless, Z light yellow. It is estimated that above J, the shade of yellow will only be noticeable to the naked eye by a trained eye.

The quality of Cut

Brilliance (light return) and fire (dispersion) of a diamond depend on the quality of cut. The assessment of quality of takes into account three main parameters: proportions, symmetry, and polish. Classifying the size itself is a complex exercise for an inexperienced person, so it's best to rely on reports from large labs. In a quality report, each of these parameters are rated as follows: - Excellent, Very Good, Good, Fair, and Poor. According to the AGS (American Gem Society), a very well-cut diamond can be worth up to 50% more than a diamond with a medium cut quality.

Treatments

It is important to ensure that a diamond has not undergone any treatment, which could decrease its value. The most common treatments are:

• Fracture Filling. For a long time, it was "exclusive" to emeralds, but since 1987, diamonds can also be treated in this way, as are some rubies more recently. The treatment can be detected under a microscope by a flash effect or colour reflections and/or bubbles in the filler material.
• Laser Drilling. A laser is used to drill a very thin tube into the diamond reaching dark inclusions. Chemicals are then injected, making the inclusions much less visible. The treatment is easy to detect under a microscope and is permanent.

Imitations and Synthetics

In addition, it is important to make the consumer aware of imitation diamonds available on the market, such as natural colourless stones (sapphire or zircon), or synthetic stones made in laboratories, such as colourless synthetic spinel. Regardless, these stones do not have the same brilliance or dispersion as diamonds. The two most common imitations found on the market are cubic zirconia (also known as CZ, dating back to the 1980s) and synthetic moissanite (first seen in 1998). Until the arrival of synthetic moissanite, it was easy to recognize a diamond from its imitations thanks to a detector based on thermal conductivity (diamond being a much better conductor than its imitations). This is no longer the case due to synthetic moissanite, however, various brands now manufacture a tester that can differentiate between the three. It is important to check the tester to be sure that it is completely reliable (i.e. have comparison stones) and to repeat this operation periodically. Due to potential failure by testers, the best way to differentiate is to observe the stone under a microscope.