The Grading of Diamonds: Understanding the 4Cs and Beyond

The 4Cs of Diamond Grading

Created in the mid-20th century by the Gemological Institute of America, this ‘universal’ framework for assessing diamond quality is considered the standard for diamond grading. Each of the 4Cs has its quality parameters, and each ‘C’ contributes to different attributes of the diamond.

4Cs Carat: The Weight of a Diamond

The number of carats a diamond weighs is not an indication of its size; a single carat (ct) is equal to 200 milligrams (0.2 grams). Diamonds are weighed on scales calibrated to the hundred-thousandth of a carat with extreme precision. Carat weight is the only one of the 4Cs that is a simple measurement comparison – two diamonds of equal weight can be very different from one another depending on the other grading factors. Most would assume that a higher carat weight equates to a larger diamond, but this is not the case. Because of the way a diamond is cut, as well as its depth and surface area, it can appear larger even though it might have less actual carat weight. For example, a perfectly cut diamond can appear larger than a poorly cut diamond of the same carat weight. Because larger diamonds are less common, a diamond’s carat weight will increase exponentially in value with size. So, for example, a two-carat diamond will typically cost much more than two one-carat stones of the same quality.

4Cs Cut: The Diamond’s Brilliance

Cut is often called the ‘king’ of the 4Cs because it plays the biggest role in to how brilliant a diamond appears. While the carat, color, and clarity are dictated by nature, the cut of a diamond is the only human factor. Cut determines how well the rough stone has been transformed into a polished gemstone through muster-cutting and faceting, or cutting and polishing, to achieve optimal light emission – reflection and refraction that makes the stone glitter. The GIA grades diamond cuts on a scale of Excellent, Very Good, Good, Fair, and Poor, looking at its overall appearance for brightness, fire, scintillation, and symmetry. Brightness refers to the whiteness that is reflected from the diamond, while fire is when light is dispersed into colors, and scintillation is when the stone becomes extraordinarily bright and sparkly when it is moved. A diamond that is well-cut will reflect the greatest amount of light from its facets and will appear brighter and more colorful than most diamonds. The underlying characteristic of a good cut is its relative proportions, especially the depth and the table size, which both contribute to how much light a diamond reflects. If too shallow or too deep, diamonds will leak light from the bottom, making them look less brilliant. Ideal cuts are designed to bounce light back through the top of the diamond.

4Cs Color: The Absence of Hue

When the word “color” is used in the context of a diamond, it is almost always referring to the absence of color. In other words, the more colorless a diamond is, the more light is transmitted through it – and the more light is transmitted, the more rainbow flashes are reflected out, making the diamond essentially appear more brilliant, as more light is involved with each reflection produced. The GIA grades diamonds on the D-to-Z color scale, from colorless to light yellow, or brown. The color grades differ subtly but the colors significantly impact the diamond’s price and appearance: a D-grade diamond is colorless, extremely rare, and therefore, more expensive. If you go down the scale, the stone will take on more noticeable lemon or brown tones, which will affect appearance and value. Some fancy-colored diamonds that are extremely rare and exhibit intense hues of blue, pink, green, or yellow are valued primarily because of the intensity of their color. Fancy color diamonds are graded differently from white diamonds.

4Cs Clarity: The Diamond’s Flawlessness

Clarity refers to the extent to which internal inclusions and/or external blemishes impair how light moves through the diamond, ultimately reducing the amount of brilliance. Inclusions are imperfections found within the diamond, such as air bubbles, cracks, or materials other than the diamond itself, whereas blemishes are surface flaws. The GIA grades clarity on a scale from Flawless (no inclusions or blemishes visible under 10x magnification) to Included (inclusions and blemishes that are easily visible to the naked eye). The GIA’s clarity scale includes the following grades:

Flawless (FL): No inclusions or blemishes visible under 10x magnification.

Internally Flawless (IF): No inclusions visible under 10x magnification; only minor surface blemishes.

Very, Very Slightly Included (VVS1 and VVS2): Inclusions extremely hard to see with 10x magnification.

Very Slightly included (VS1 and VS2): Inclusions are minimal and difficult to observe under 10x magnification.

Slightly Included (SI1 and SI2): Inclusions are noticeable under 10x magnification.

Included (I1, I2, and I3): Inclusions are obvious under 10x magnification and will most likely affect the durability and brilliance of the diamond.

Clarity also makes a difference because diamonds with fewer inclusions are rarer and therefore worth more. Although most inclusions are so small that they cannot be seen with the naked eye, diamonds in the top invisible VS range are more valuable than those in the SI range, with inclusions that are still not visible without a magnifying glass. The VS diamonds, especially those with no visible inclusions or with only internal flaws, can seem to have a magic of their own. But for most buyers, diamonds in the VS or SI range offer a good balance between appearance and affordability. Other factors such as polish and symmetry can also affect its overall grade and value beyond the 4Cs.

Fluorescence

Under UV light, fluorescence is when a diamond appears to have a soft glow. The fluorescence grade extends from None to Very Strong, issued by GIA (the Gemological Institute of America). In most cases, the fluorescence isn’t detectable under normal lighting conditions, and its effect on the appearance of a diamond is negligible, too. That said, strong fluorescence, in some cases, can cause a diamond to appear milky or hazy. On the other hand, in lower colors, a faint blue fluorescence helps a diamond to appear whiter, masking the yellowish tints in the stone.

Polish and Symmetry

Polish and symmetry impact the overall finish. Polish involves the smoothness of the facet surface; symmetry refers to the symmetry of facet alignment. Each of these factors are independently graded on a measure of Excellent, Very Good, Good, Fair, and Poor. Excellent or Very Good polish and symmetry will reflect light more evenly and possibly give a higher overall grade.

Diamond Grading Reports

If buying a diamond, it is always important to obtain a grading report from an accredited laboratory such as the GIA, the American Gem Society (AGS) or the International Gemological Institute (IGI). These reports are highly descriptive of every aspect of the 4Cs, as well as fluorescence, polish, symmetry and virtually every other attribute. A grading report also gives buyers peace of mind that the diamond’s quality has been independently verified.

The Diamond Market

The 4Cs (carat, cut, color, clarity) all come into play during the grading process, as do a number of other factors, such as fluorescence and symmetry. The more you learn about these aspects of a diamond, the easier it will be to choose wisely the next time you’re in the market for one. Whether you’re looking for a GIA Flawless piece of jewelry or just another gorgeous addition to a jewelry collection, check out Diamond by Raymond Lee’s website to see the latest high-end jewelry.