The Four C's

Find out what's important to know when you are looking for your diamond.


This, of course, is the first thing people think of and notice about diamonds, especially engagement rings. "How big is it?" is often the phrase that follows "Congratulations!" when you hear that someone is engaged. However, "bigger is better" is not always the best advice when selecting a diamond.

The Optical Illusion

The Optical Illusion relates to how a stone is cut as well as its carat weight. A diamond can actually be cut to look bigger than it is. For example, a properly cut round brilliant diamond that weights about one carat should be approximately 6.5 mm across. However, a stone weighing much less than that could be cut too shallow to make it appear as large as the properly-proportioned stone. Some jewelers may try to put a higher price on this stone, because it appears to be larger than it really is.

The opposite can also occur when a stone is cut too deeply, but weighs the same as a properly cut stone. In both cases, the poorly cut stones cost the jeweler less, but are sometimes not discounted to the public accordingly.

The Optical Illusion is one very good reason to always buy certified stones graded by independent laboratories. The stone is evaluated by a third party that is not financially invested in the quality or size of the stone. This means you get an unbiased evaluation.

Diamond Math

Everyone knows that a bigger diamond is more expensive, but the price increases are not that straight-forward. For example, a one carat diamond should cost about twice as much as a similar half-carat diamond, right? Not true. The price of a diamond increases exponentially as the size goes up. So, if the half-carat stone costs $5, then a one carat stone would cost $15 and a two carat stone would cost $50.

Big Points and Big Leaps

There are certain points as a diamond's size increases where the price does even more gymnastics. For example, going up two to four points doesn't usually have a great impact on the price of a diamond. However, if that increase crosses any of the "big points," the price will take a "big leap."

1.00, 2.00 The whole-carat marks are obvious points where the price of a diamond will make the biggest leaps in price.
0.25, 0.50, 0.75 The quarter-carat marks also create obvious "big points" where price may leap.
0.33, 0.65, 0.90 These are less obvious points where price may leap. These leaps will be the smallest.


The number, size, type and location of imperfections in a diamond determine its clarity. These imperfections come in many forms: black piques, feathers and clouds to name a few. Below is the rating system used for diamond clarity:

IF Internally Flawless
VVS Very, Very Slightly Included (1, 2)
VS Very Slightly Included (1, 2)
SI Slightly Included (1, 2)
I Included (1, 2, 3)

The importance of clarity, as with all of the four C's, is subjective. Some people value clarity over color or carat, while others may put carat above anything else. It all comes down to individual preference.

The non-subjective importance of clarity lies in whether the imperfections affect the appearance of the stone. Diamonds with a clarity grade of VS and above are not greatly affected by the imperfections because they can only be seen with magnification. Imperfections do not affect the "sparkle" of a diamond unless they are large enough to obstruct light within the stone.


Letters are used to grade the color of diamonds. The letter D is used as the highest or whitest rating. As you move down through the alphabet, the color becomes darker, moving to yellow. RED letters indicate the best range for engagement ring diamonds.

Near Colorless
Faint Yellow
Very Light Yellow
Light Yellow

The Gemological Institute of America has provided the industry with the most comprehensive system for evaluating the different color grades. Those colors range from D-Z in the alphabet and then move into the "fancy yellow" grades. They also have a grading for diamonds that have "fancy" colors like green, blue, pink, brown and red.

More Than Just White

This color grading system does not include the many "fancy" colors of diamonds. The most popular are fancy yellows, pinks and blues. Other colors include green, red and orange. These fancy-colored diamonds are more rare and therefore more expensive than traditional white stones.

Lately, previously industrial or commercial-grade diamonds have found new life as champagne, burgundy and chocolate-colored diamonds. Even black diamonds are gaining popularity in fine jewelry.


Cut is perhaps the most important of the four C's. It is the cut of a diamond that releases its brilliance. A well-cut H, SI stone will look better than a poorly cut E, VVS stone when they are placed together. The facets are what create the sparkle and scintillation of a diamond, assuming that the color and clarity are of a responsible grade, i.e. not industrial or commercial grade.

Grading the Cut of a Diamond

Just as color and clarity have a grading system, so does cut. In 1919, Marcel Tolkowsky calculated proportions that have become the benchmark for cutting round, brilliant diamonds called the "Ideal Cut" or "American Cut Ideal Brilliant."

The most widely recognized grading laboratories have developed their own terminologies in evaluating cut. Some are: excellent ideal cut, Tolkowsky ideal cut, AGS 000 and premium cut. All of these terms represent proportions ranging from poor to fair to good to very good to excellent.


Here are some specifics on shape:

Round This is technically the most brilliant of the diamond shapes.
Princess Cut This is a square-shaped stone and is the second-most brilliant. It is also the second in popularity to the round brilliant.
Emerald Cut This shape has the fewest facets. Because of this, it is usually best to stick with a higher color and clarity rating. Though it has the fewest facets, it is a very elegant and traditional shape.
Pear, Oval and Marquise These shapes have one inherent flaw known as the "bow tie effect." Due to the way the diamond must be cut to form these shapes, they exhibit a dark bow tie shaped area in the center of the stone. This is more obvious in poorly cut stones. Look for this and choose a diamond that minimizes this effect.
Heart Shape This is a very unique cut that is not easy to create. This may increase the price of a diamond compared to some of the other fancy shapes.