All of the 4 Cs are not equal; some are more important than others. And, by far, CUT is the most important C in diamond buying.
It is the only one of the Cs that is completely in the hands of the expert craftsman who transform a rough stone into sparkling gem, and the quality of diamond's cut is responsible for as much as 50% of the final price of a diamond.
The other factors of a diamond's quality (color and clarity) are determined by nature during the diamond crystal's formation.
Cut is also the C that determines how well each diamond does what it's supposed to do, which is... Sparkle like crazy.
Have you ever seen a diamond that looks dull and lifeless? That is typically because the diamond was cut poorly, either too deeply or too shallowly (more on this below).
On the other hand, have you ever seen a diamond so sparkly that you can't help but notice it and admire it, even from across the room? That diamond was expertly cut. And not only will a well-cut diamond be noticeably more beautiful, it will also hold its value better over time.
So, when you're thinking about buying a diamond, it's easy to get carried away with size, but cut is truly what will set your diamond apart and give you more value for years to come.
When we talk about the "cut" of diamond in the context of the 4 Cs, we are not talking about the diamond's shape (like round, princess cut, oval, emerald cut, etc.).
When we talk about diamond cut in relation to the 4 Cs, we are talking about:
How well the diamond is cut to sparkle.
In technical terms, what is happening is light refraction.
Remember in science class when you aimed a light at a prism and the colors of the rainbow came out the other side? That's refraction. That's what's going on when you see a diamond sparkle.
In a well-cut diamond, light flows into the top of the diamond and is refracted back out of the top in it's beautiful spectral colors (which we see and describe as "sparkle").
You can see in the diagram that in an ideal cut diamond, the light enters the top and returns back out the top.
In contrast, when a diamond is cut too "deep" or too "shallow," light is lost out of the bottom or sides of the diamond.
The result is a diamond with significantly less sparkle, which can look dull and lifeless. Not good.
This is why the "Ideal Cut" round diamond is by far the most popular. Ideal Cut a mathematically precise way to cut a diamond for maximum beauty and sparkle.
If you're buying a round diamond, look for "hearts and arrows." When an ideal cut diamond is examined under specialized tools, it displays a pattern known in the industry as "hearts and arrows," which look like this:
That is what a round diamond looks like that is symmetrical and ideally proportioned for maximum sparkle. A good jeweler will often be able to show you the diamond under this specialized view so you can see the cut of the diamond for yourself.
On diamond grading reports, quality of cut is typically represented on a scale from "Poor" to "Excellent," or "Poor" to "Ideal".
Many people call diamonds with this type of documentation "certified diamonds," and we want to offer a word of caution here:
Be very careful with diamond "certificates."
What many jewelers don't tell you is that there is no such thing a "certified" diamond. What most people call a "diamond certificate" is actually a diamond laboratory grading report.
And at the end of the day, a grading report is just someone's opinion of the quality of that diamond.
And, inside the industry, it's common knowledge that most diamond grading reports are NOT reliable. Many of these "grading laboratories" intentionally represent stones as a higher quality than they really are.
There are two main reasons for doing this, and neither one is good:
The jeweler may be trying to get a higher price for a lower quality stone.
Or the jeweler may be charging a reasonable price for the actual quality of the stone. But by showing a "certificate" saying that the stone is higher quality than it is, they can create the impression that customer is "getting a deal."
In both cases, it doesn't matter what the paper says. The diamond is what it is and the "certificate" is nothing more than an inaccurate opinion.
Inside the jewelry industry, as a general rule, there are only two grading laboratories that are consistently trusted to be accurate: The American Gem Society (AGS), and the Gemological Institute of America (GIA).
These organizations set the bar for grading accuracy and consumer protection.
However, there have been many instances of GIA and AGS diamond grading reports being forged, copied, and manipulated by wholesalers and retailers over the years.
So, again, be very careful with diamond grading reports. They can be great additional documentation of the quality of your diamond, but a grading report alone should not be how you buy a diamond.
There's a reason that no good jeweler buys diamonds based on grading reports. Every good jeweler I know physically handles and evaluates a diamond before buying it for their inventory, or selling it to a customer, no matter what the grading report says.
Everything we've said here can be easily summed up:
If you want a diamond that's visibly more beautiful, that sparkles noticeably more than an average diamond, you need to buy a diamond with good to excellent cut.
Grading reports can be helpful, but at the end of the day you want to work with a jeweler you trust, who selects their diamond inventory based on quality of cut.
Cut is by far the most important C. Cut gives you more beauty and sparkle, and it gives you more value for your dollar than any other C.