Diamond Grading: What Qualities Matter Most?

You’ve probably heard of the 4 Cs of diamond grading. I’ve ranked them below, in terms of importance when you choose a diamond.

Cut: The most important property.
Color: The second most important property.
Clarity: The third most important property, provided the grade is “SI” (Slightly Included) or better.
Carat: The least important property.

Now, we’ll go through the evaluation of each property.

The Cut

One of the hardest properties to judge, the cut is nevertheless the most important. Choosing a well-cut diamond requires paying careful attention to a few key characteristics.

Brilliance: Brilliance refers to the total amount of light returned by the gem. A cut gem’s pavilion facets should act as mirrors, reflecting the light entering the stone back to the observer. The cut plays a critical role as the angles at which a diamond is cut affects greatly how efficiently it reflects light as this impacts how well the diamond sparkles. Unfortunately, diamond cutters can’t cut all mined diamonds to excellent proportions. Often, they must compromise between maximum brilliance and maximum yield (weight/carat retention). If cutters remove too much material from the diamond rough, they may cut away their profit. Thus, for economic reasons, many diamonds receive a cut with less than ideal proportions. However, if a cutter varies a little further from the ideal cut angles, the diamond’s brilliance begins to suffer. If the cutter varies too far, you’ll get a diamond that just doesn’t compare to others in brilliance or fire.

The Make of a Diamond: The Gemological Institute of America (GIA) and other certifying bodies assign cut grades to round brilliant cut diamonds. Despite this, no grades on any certificate can effectively evaluate the cut. Most jewelers, familiar with correct proportions, can judge the cut from the shape of a diamond. In the jewelry trade, they call it the “make” of a diamond. A “heavy make” means the stone was cut to retain weight at the expense of a good cut. A “spready make” means the stone appears, “face-up,” to weigh more than it actually does. Such a make can sometimes impact the cut as well. By simply comparing gems side by side serves as the best test. If you have two diamonds of the same grade, but one is significantly brighter, the cut makes the difference.

Non-Round Diamond Cuts
Please understand, the information above assumes we’re talking about round diamonds. Cutters can cut all their major facets at the same angle due to the round’s symmetrical proportions. For other shapes, this doesn’t hold true. For example, many people prefer a marquis shape. This is fine, but don’t expect a marquis, or any other shape, to have the brilliance of a round. A marquis requires cutting a number of facets just to accommodate the shape. Cutters cut these facets at angles that vary from those that give the greatest brilliance. This is a simple fact: the more facets cut at the ideal angle, the greater the gem’s brilliance.

Diamond Shape

Another factor to consider when you choose a diamond is its shape. An ideal cut diamond should be symmetrical, not lopsided. A poorly proportioned gem can be “camouflaged” in its setting. Thus, you might not notice it until after you’ve bought it. Always examine a diamond loose, not in the setting.

Girdle Proportions and Brittleness

In terms of resisting scratches, diamonds are famously the hardest material in the world. However, in terms of resisting blows, they’re brittle. This property affects the cut evaluation, particularly when examining the girdle. A gem’s girdle is its widest part when viewed from the top but its thinnest when viewed from the side. If a gem cutter cuts the diamond’s girdle too thin, it can present a weak area, just asking for trouble. Some girdles get cut to a knife-edge level of thinness. Definitely avoid this, because it can cause the gem to fracture or break.

Diamond Color

The closer to colorless, the greater a white diamond’s value. GIA’s color grading system for white diamonds begins with the letter D and goes to Z.

D, E, and F: The highest grades for white diamonds. These colors are described as colorless.
G, H, I, and J: These colors are described as “near colorless” or white.
K to Z: These colors are described as tinted, usually yellow or yellowish brown. Diamonds with colors K, L, or M are often said to “set white.” That means, if jewelers set them in yellow gold, the stones will appear white, since they have only slight tints. However, white gold or platinum settings would set off the tinted colors.

The further the grade goes down the alphabet, the stronger the tinting and lower the diamond’s value. However, once you get to the extreme end and the color becomes richer, you have a fancy colored diamond. No longer considered “off colored” white diamonds, their value starts going up again.

Clarity

The size and number of inclusions inside a diamond determine its clarity. An inclusion can be another mineral, a fracture, or occasionally a void. Simply put, anything that will interfere with the free passage of light in a gem qualifies as an inclusion. The highest grade a diamond can get is flawless. That means you can see no inclusions at 10X magnification. However, this doesn’t mean you can’t find inclusions with higher magnification. Also, don’t assume it’s the only grade with no inclusions visible to the naked eye.In addition to F for flawless and IF for internally flawless, clarity grades use the letters V,S & I. They stand for Very, Small, and Inclusion. Numbers 1 to 3 further designate levels within grade.

After F and IF, clarity grades proceed as follows:

VVSI1 (Very, Very Small Inclusions One)
VVSI2
VSI1
VSI2
SI1
SI2

All these clarity grades indicate diamonds with no inclusions visible to the naked eye. These are all eye clean. Further down the grading scale, you’ll find I1 and I2 diamonds. These have eye visible inclusions. However, they’re still considered gem grade.

When is a Diamond Not a Gem?

You may encounter diamonds so heavily included that they are not usually considered gem grade, because so little light will pass through them. However, since they still have the magic name “diamond,” they do show up on the market regularly.

Before you choose a diamond, beware of ads promoting a 1-carat diamond ring for a very low price. Not all diamonds are considered gems. Nevertheless, the vast majority of mined diamonds are usually considered industrial grade.

Carat

By far, carat or weight is the easiest quality factor to understand when you’re shopping for diamonds. Simply put, small diamonds are more common than large ones, but larger stones are more desired. Therefore smaller diamonds cost less per carat than large ones. This explains why you’ll encounter jumps in price per carat as diamond sizes increase.

Can You Get Better Value with a Lower Quality Diamond?

Occasionally, looking for a lower clarity graded diamond may be worthwhile. This depends on the individual diamond and setting. Sometimes, the eye-visible inclusion that made it rank lower may have an insignificant effect on its appearance. Overall, the stone may still look delightful.

However, going down further in quality in other areas is rarely worthwhile. Without making a comparison with better quality diamonds, customers often convince themselves they’ve found a great deal. When they make the comparison later, they find disappointment.

Does Size Matter?

Selecting a diamond is a personal thing. Of course, not everyone will have the same opinions. However, consider this observation carefully before you choose a diamond. In my experience, most folks will enjoy a smaller, higher quality dazzler more than a larger but mediocre gem.

Some Differences Matter More

Let’s say you look at two well-cut diamonds side by side. One has grades of D and VVSI1. The other, G and SI1. With the naked eye, you wouldn’t see much difference, if any. However, you’ll likely have a strong emotional reaction when you compare their prices. The point is simple. These are the rarest quality diamonds. Only a sophisticated diamond appraiser who inspects them carefully under magnification will appreciate their differences.

Summary

To summarize, when you choose a diamond, go with quality rather than size. Also, keep in mind that the differences between the rarest quality diamonds may not be worth the price (or even perceptible to anyone but an expert).