A woman shows off her engagement ring and wedding band.

Featured jewelry: Acclaim Engagement Ring

Which of the 4 C's Matters the Most? Hint: It's Not Carat

By Jack Busch

You go into a jewelry store, and the associate behind the counter shows you two diamonds and asks you to pick the more valuable one. Easily, you point to the one on the right. It looks bigger. It has more sparkle and vibrancy. It simply looks more alive. Then, to your surprise, the jeweler tells you the one you picked is actually smaller and fewer carats than the diamond on the left.

How can this be? It's all about the 4 C's (color, clarity, cut, and carat weight) and how they work together. On paper, they are graded to determine the value of the diamond. However, when you behold an actual diamond in the light, the interplay among them is obviously much more complex.

Rating the 4 C's

To rate the 4 C's, the Gemological Institute of America uses terminology-based scales and the American Gem Society uses numerical scales. Based on that, it seems like choosing a diamond should be fairly simple: Choose the one that offers the best overall 4 C's rating at the best price. If you think that, you're on the right track—it's important to look at more than just the carat weight—but you aren't quite there.

The reality of diamond shopping is that quality jewelers will rarely show you a diamond that isn't colorless and flawless. When you get that high up on the scales, a point here or there isn't going to make a huge difference in the value or look of the diamond. At that point, it's all about the cut.

Don't mistake cut for shape. This is not an objective data point, like carat weight. On a diamond grading report, the cut rating is a judgment of the quality of the cut. When a diamond is cut, the goal is (or should be) to get the exact proportions that are going to yield the best possible light performance—that is, how the diamond catches the light and refracts it into that dazzling magical sparkle that is quintessential to the conception of an ideal diamond. The number of facets, the angle of the facets, and the symmetry of the shape all play into the light performance of the diamond.

The Ideal Cut

Achieving an ideal cut involves both art and science, and neither should be sacrificed. For instance, many diamond cutters tailor the cut so the carat weight stays above 1.0 carats. However, this is a mistake. For each diamond, there are specific ideal proportions that will make the diamond sparkle at its best, and it is far better to have an ideal cut diamond that is 0.9 carats than a poorly cut diamond that is 1.0 or 1.1 carats.

Besides, when passersby admire the ring, the last thing they'll be looking at is the paperwork. Nobody ever comments about the clarity or color or carat weight—they "ooh" and "aah" at what they can see: the sparkle.

It certainly pays to understand the 4 C's and why they matter. However, at the end of the day, lavish attention on the cut, since the sparkle is what truly determines the beauty and value of a diamond. When nature creates a colorless, flawless diamond over millions of years, that's a miracle. When someone cuts that diamond into something even more beautiful and valuable, that's craftsmanship.