Cut is perhaps the most important of the four Cs, so it is important to understand how this quality affects the properties and values of a diamond.
The angles and finish of any diamond are what determine its ability to handle light. A good cut gives a diamond brilliance (the brightness that seems to come from the very heart of the diamond) and scintillation and dispersion (the sparks of color that seem to leap out from the diamond’s surface when the diamond is tilted back and forth).
[Don’t confuse Cut with Shape. Cut refers to how well the diamond has been designed and proportioned by the cutter. Shape refers to the general silhouette or outline of the diamond. For more on shape, click here.]
As you can see in the images below, when a diamond is well-cut, the light that enters through the table travels deep into the pavilion. Once light reaches the pavilion, it bounces back and forth on the mirror-like inside walls of the pavilion, multiplying in brightness and intensity before reflecting back out of the diamond through the table and to the observer’s eye.
To understand how the pavilion works to make a diamond so brilliant, think of an empty room that has a single candle as its only source of light. If a mirror is added to the room, the mirror will reflect the image of the candle, creating a second image of the flame and essentially doubling the amount of light in the room. If more mirrors are added to the room, the brightness in the room will increase as the number of reflections of the original candle flame increases. A well-cut diamond works in much the same way as a series of mirrors that multiply the brilliance of the original light source. This light is the brilliance we mentioned, and it’s this effect that makes diamonds so mesmerizing.
However, when a diamond is poorly cut (either too shallow or too deep), the light that enters through the table reaches the pavilion facets at the wrong angle and fails to be intensified and reflected properly; it ‘leaks’ out from the sides or bottom of the diamond rather than reflecting back through the table to the eye. Less light reflected back to the eye means less brilliance.
There is no single measurement or proportion that automatically makes a diamond beautiful. Rather, a great cut depends on the carefully-planned interaction of many proportions to create a diamond’s beauty and ability to handle light.
These are the main proportions that help to determine a diamond’s cut:
Diameter: The length and width of the diamond as measured across the girdle. Primarily, the Diameter gives you an idea of the diamond’s physical size, but it is also used as point of comparison to calculate the diamond’s table percentage, total depth percentage, crown height, and pavilion depth.
Table: This is the large, flat facet at the very top of the diamond. Table size or table percentage describes how large the table is in comparison to the diameter of the entire diamond. For example, a 57% table is a table that is 57% as wide as the diamond’s diameter. Most jewelers tell customers that a small table is best, and many customers do like the look of a small table. However, a small table is not critical to a diamond’s brilliance and, in fact, there are many round diamonds that have tables of 60% or even 62% that achieve a GIA cut grade of Excellent.
Crown: The upper portion of a cut gemstone, above the girdle. The crown height describes how deep the crown is in comparison to the width of the diamond’s diameter. The crown angle describes the angle at which the bezel facets intersect with the table plane. The angles and proportions of the crown create the effect known as dispersion.
Girdle: The narrow rim of a diamond that separates the crown from the pavilion. It is the widest part of the stone. A good girdle should be thick enough to protect the diamond at its vulnerable edges. A girdle that is too thin will leave the diamond vulnerable and also make it difficult to set in jewelry; a girdle that is too thick will needlessly add extra mass and carat weight to the diamond without increasing the diamond’s diameter in millimeters.
Pavilion: The lower portion of the diamond, below the girdle. The pavilion depth describes how deep the pavilion is in comparison to the width of the diamond’s diameter. The pavilion angle describes the angle at which the pavilion main facet plane intersects with the table plane. The angles and proportions of the pavilion help to create the effect known as brilliance.
Depth: The height of a gemstone, from the culet to the table. Total depth or depth percentage describes how deep the diamond is in comparison to the diameter of the entire diamond. The diamond should be deep enough to adequately absorb and reflect light. If the diamond is too shallow, the light will not be effectively reflected; if it is too deep, the diamond may not reflect the light properly and it will also “waste” carat weight in the bottom of the diamond where it cannot be seen instead of contributing that weight to the size or diameter of the diamond.
Culet: The tiny facet on the bottom of the pavilion. When it exists, this is usually the smallest facet on the diamond and it is intended to protect the pointy bottom of the diamond from becoming chipped or damaged. However, some diamonds do not have a culet at all and just end in a point at the bottom of the pavilion. Once a diamond is mounted, the pavilion is protected by the setting, so the presence or absence of a culet will not really affect the appearance or durability of most diamonds.
Everyone knows that the angles and proportions of the crown and pavilion facets determine whether a diamond will be bright and lively or dark and lifeless. So, if a 57% table and 34 degree crown angle look wonderful on one diamond, why isn’t every diamond cut exactly the same way?
The simple answer is that there is no such thing as a ‘one size fits all’ approach to diamond cutting. Each diamond is a one-of-a-kind custom-designed creation.
One reason is that, even with the new research and lab-assigned cut grades that are available, different people have different ideas of what makes a diamond beautiful. For example, some people like very small tables of 53% or 54% and some people like larger tables of 58% or 60%. Sometimes the reason for a particular diamond’s appeal isn’t even something that an individual can articulate; the diamond simply ‘speaks’ to that person. Think of a jewelry store with 10 diamonds lined up on the countertop, all weighing .50 carats, all with G VS1 quality, and all certified by AGS as Ideal Cut diamonds. If 10 people were asked to pick their favorite diamond from among this group, it is unlikely that all 10 people would identify the same exact diamond as their unanimous favorite. So, while well-cut diamonds should conform to a certain range of proportions, they don’t all have to be cut to only one exact set of proportions. Beauty can be found in many subtly different forms.
Even if we could get everyone to agree on one exact set of ‘perfect’ measurements, creating the perfect cut is extremely difficult. Rough diamond crystals vary widely in shape, weight, and clarity when they come out of the earth. The ideal natural shape of a rough diamond is an octahedron (an 8-sided crystal that resembles 2 pyramids stuck together base-to-base). In reality, though, most rough diamond crystals have strange irregular shapes and indentations that create limitations on what type of polished gem can be created out of them.
A diamond cutter has to decide what type of diamond shape (for example, round, pear, or emerald cut) the rough crystal is suited for: a long thin crystal isn’t suitable for making a round diamond, but it would be just right for creating a pear or marquise; and a stone that is relatively flat from top to bottom won’t be deep enough to use for a radiant (which depends on a deep pavilion to create the proper brilliance) so it might be used to create a trilliant, which requires more shallow proportions.
The cutter also needs to consider how he can create the largest possible polished diamond out of the existing rough so that he doesn’t waste any of the valuable crystal.
And, as if that wasn’t enough, he must decide which set of proportions and variations in design will allow him to achieve the highest clarity that is possible. Most diamonds contain at least some inclusions, which are spread out randomly throughout the stone. The cutter’s goal is to find a way to eliminate the parts of the rough crystal that contain large inclusions and to design the diamond so that the remaining inclusions will be located off to the edges or in the pavilion of the polished gem, where they are less likely to be visible to the naked eye.
A diamond cutter must consider all of these factors—shape, carat weight, clarity—while still striving to create a diamond that is symmetrical and well-proportioned. Since each rough diamond has its own natural variations, the “solution” to creating a great stone has to be reinvented with every new rough crystal.
All of these considerations mean that there is no hard-and-fast description of the ‘perfect’ cut for a diamond. Because of this, it can be extremely difficult for the average consumer to figure out which diamond is the best choice.
To make the process of choosing a diamond easier, Mondera provides a cut grade for every certified loose diamond in our Diamond Store.
All of the loose diamonds in our Diamond Store are certified by either GIA or AGS. Both of these labs have developed grading systems that help consumers to evaluate round diamonds’ quality of cut. In situations where a GIA or AGS cut grade is not available (that is, if a diamond is fancy shaped, or a round diamond certified by GIA before 2006) Mondera provides a cut grade to allow you to compare the diamonds.
How GIA Grades Cut
GIA’s cut grading system considers 7 qualities: Brightness, Fire, and Scintillation (which are considered the Face-Up Appearance components of the cut grade); Weight Ratio and Durability (the Design components); and Polish and Symmetry (the Craftsmanship components). GIA rates the Cut of diamonds as either Excellent, Very Good, Good, Fair, or Poor.
How AGS Grades Cut
AGS’s cut grading system considers 11 qualities: Brightness, Dispersion, Leakage, and Contrast (the Light Performance components); Durability, Tilt, Weight Ratio, Girdle Thickness, and Culet Size (the Proportions components), and Polish and Symmetry (the Finish components). AGS rates the Cut of diamonds as either Ideal, Excellent, Very Good, Good, Fair, or Poor.
How Mondera Grades Cut
If a diamond does not have lab-assigned cut grade from GIA or AGS, Mondera considers 6 qualities in order to determine the appropriate cut grade: Depth Percentage, Table Percentage, Girdle Thickness, Culet Size, Polish, and Symmetry.
Ideal
Diamonds that are described by Mondera as Ideal have a make which is considered fine by anyone in the industry. This cut is intended to maximize brilliance, and the typically smaller table sizes of these diamonds have the added benefit of creating a great deal of dispersion or ‘fire’ as well. Ideal quality diamonds are truly for the person who enjoys knowing that he has one of the finest things that money can buy.
The Ideal cut grade includes diamonds that are graded as AGS Ideal or GIA Excellent, and diamonds that have been assigned an Ideal cut grade by Mondera.
Very Good
Diamonds that are described by Mondera as Very Good are of an excellent make. They reflect most of the light that enters them, creating a good deal of brilliance. With these diamonds, the cutters have chosen to stray slightly from the preferred diamond proportions in order to create a larger diamond. The result is that these diamonds fall slightly outside of some customers’ preferences in terms of, for example, table size or girdle width. In many cases, though, many of the proportions of diamonds in this range will overlap with certain proportions of diamonds in the Ideal range. Generally, the price of these diamonds is slightly below that of Ideal cuts.
The Very Good cut grade includes diamonds that are graded as AGS Excellent, AGS Very Good, or GIA Very Good, and diamonds that have been assigned a Very Good cut grade by Mondera.
Good
Diamonds that are described by Mondera as Good reflect much of the light that enters them. Their proportions fall outside of the preferred range because the cutter has chosen to create the largest possible diamond from the original rough crystal, rather than cutting extra weight off to create a smaller Very Good quality diamond. Diamonds in this range offer an excellent cost-savings to customers who want to stay in a budget without sacrificing quality or beauty.
The Good cut grade includes diamonds that are graded as AGS Good or GIA Good, and diamonds that have been assigned a Good cut grade by Mondera.
Fair and Poor
A diamond that is graded as Fair or Poor will reflect only a small proportion of the light that enters it. Typically these diamonds have been cut to maximize the carat weight over most other considerations. We do not recommend this type of cut. To ensure that our customers enjoy only fine, classic jewelry, Mondera does not offer diamonds that have been graded as Fair or Poor.
Want to know the full story behind Ideal Cut diamonds?
Click here for an in-depth explanation of the mechanics and formulae that led to the Ideal Cut.
Diamonds come in all kinds of shapes, including round, heart and princess cut diamonds. To learn more about different diamond shapes, click here