Diamonds undergo cutting to enhance their sparkle, fire, brilliance, and overall visual appeal. The cut is crucial as it directly influences how light interacts with the diamond's facets. Before cutting and polishing, diamonds exist as rough stones with opaque surfaces that inhibit light transmission and sparkle. The transformation from rough to polished diamond involves creating facets that allow light to enter, reflect, and refract within the stone, resulting in the characteristic sparkle.
Light performance in diamonds occurs when light enters, bounces around within the diamond, and returns to the eye. The angles, sizes, locations, and shapes of facets determine how effectively this light performance is achieved, impacting the diamond's sparkle. Thus, the cut of a diamond plays a pivotal role in maximizing its brilliance and visual allure.
TABLE OF CONTENTS |
| Cut Scale: The Factors |
| The Cut Scale |
| Light Performance |
| Finish: Polish, Symmetry and Facets |
| Pricing Effect |
| Selecting Cut Grade |
| Parts of a Diamond |
| Diamond Brilliance: What Makes Sparkle |
| Diamond Cut History |
| The Diamond's True Size or 'Spread' |
| Expert Buying Tips |
Cut Scale: The Factors
After a diamond is cut and polished, its cut quality can be evaluated and graded. The Gemological Institute of America (GIA) assesses cut by precisely measuring the angles and dimensions of the diamond's facets. These include the Table (top flat facet), Depth, Girdle (outer edge), Pavilion (bottom part), Crown (top part), and Culet (bottom point). Additionally, Polish and Symmetry also play roles in the overall cut grade of the diamond.
These factors collectively determine how well a diamond handles light and thus its brilliance. Each diamond shape and size has an ideal set of proportions that maximize its beauty and sparkle. If you're seeking an ideally cut diamond, consulting with a gemologist can help identify diamonds that meet these ideal proportions.
The Cut Scale
Fair & Poor: Diamonds with significant light leakage earn a Fair or Poor grade. These diamonds tend to leak noticeable amounts of light from being too deep or shallow in height. They have little brilliance and are less visually appealing. Fair or Poor cut diamonds do not meet With Clarity’s minimum light performance criteria. This cut category represents the top 35% of gem quality diamonds. Avoid these diamonds as they will not make for sparkling jewelry.
Good: Well-cut diamonds that capture light and possess high degrees of sparkle. Good cut diamonds have some light leakage but overall shine brightly. These diamonds can have noticeably larger or smaller measurements than perfectly cut diamonds of the same shape. Cutters may intentionally cut to Good proportions to achieve a particular look or style. The top 25% of diamonds have a Good cut grade. Good cut diamonds can be a good blend of value and size, but always consult a gemologist to assess the particular diamond before making a decision.
Very Good: Very well-cut diamonds that capture almost all the potential of the diamond. Very brilliant with minimal light leakage. Diamonds are often intentionally cut to achieve a Very Good grade, which can improve other characteristics of the diamond such as Color, Clarity, or Carat. The top 15% of gemstone quality diamonds are Very Good cut. Very Good cut diamonds can be a great choice if you're looking to maximize value on other factors.
Excellent: The highest grade representing the top diamonds in the world. Diamonds with an Excellent cut grade are masterfully crafted and precisely cut to unleash the maximum sparkle and brilliance of a diamond. Little or no light leakage occurs as light passes through a diamond. This premium category represents the top 3% of all diamonds. Excellent cut diamonds are increasing with improvements in manufacturing technology. An excellent cut diamond is always a good choice regardless of diamond shape and size.
Light Performance
A diamond's cut reflects the brilliance and sparkle you see from it. That sparkle is light performance, which is made up of factors such as reflection, refraction, and dispersion. The better and more uniformly a diamond is able to reflect and showcase light, the better quality diamond it is as it will sparkle more in your jewelry.
Reflections
When a diamond is rocked and tilted at different angles, some light reflects on the surface of facets rather than bouncing around inside the diamond. This is known as reflection. Typically, about 17% of light is actually reflected by the diamond. Reflection should be balanced. When facets are too large, we can see reflections either strengthen or weaken too much, which will cause the diamond to seem dull.
The ideal diamond is cut such that light enters, bounces around, bends, and ultimately exits from the top of the diamond. This concept is known as refraction. Diamonds score a 2.41 on the refractive index, which is high and gives diamonds their sparkly characteristics. With ideal cutting, the refraction is most noticeable. With a diamond that is cut well, light reflects perfectly within the diamond.
Ever noticed that a diamond isn't black and white; rather you can see all the colors of the rainbow reflecting from within the diamond? Well, that's a result of dispersion. As light bounces around in a diamond, bends and then exits back to your eye, a diamond’s dispersion is measured at 0.44. It is most commonly known as the fire within a diamond. The visibility of all these colors is what gives diamonds a unique beauty. Other gemstones and diamond simulants typically do not have the same beautiful dispersion that diamonds have. Therefore, diamonds are considered to be the most popular choice for engagement rings and jewelry.
Finish: Polish, Symmetry and Facets
Other factors that affect the cut grade are polish, symmetry, and faceting. Diamonds are typically cut in two ways: step cuts and brilliant cuts.
Step Cut
Step cuts, such as Emerald cut diamonds and Asscher cut diamonds, have sparkle or fire. They have facets that look like a staircase and are a bit simpler in presentation. They are considered very elegant and maximize the diamond's scintillation. These cuts are elegant but because they have fewer facets do not reflect light as much as brilliant cut diamonds. While both diamonds have unique beauty, it is important to consider which type of diamond sparkle you want while picking a diamond cut.
Brilliant Cut
Brilliant cuts, most commonly Round cut diamonds or Princess cut diamonds, have maximum diamond sparkle. They possess more facets than step cuts and the facets are triangular and kite-shaped. Brilliant cuts have a high degree of diamond sparkle and maximize the fire and scintillation of a diamond.
Moreover, polish and symmetry are a result of the manufacturing process. The polish of a diamond is how cleanly smooth the facet surfaces are. If small striated polish lines remain, it may affect light performance and therefore, diamond cut. The other attribute is symmetry. Symmetry is simply the pattern and evenness of the size, shape, and location of facets. If the location of a facet is incorrect, the performance of light and therefore the cut grade can be affected. For example, an off-center table facet may reduce diamond sparkle.
Pricing Effect
Like the other diamond C's, Cut grade can have substantial implications on pricing. Today, we see the highest number of Excellent cut or perfectly cut diamonds. The improvement of diamond manufacturing technology allows diamantaires to be more precise in cutting practices. With round cut diamonds, an Excellent cut can have a 5%-10% premium over the next grade, Very Good cut. The same applies from Very Good to Good.
Fancy shaped diamonds (shapes other than Round cut) do not have GIA assigned cut grades. This is because with fancy shapes, diamonds can have a variety of shapes and lengths/widths all the while still maximizing brilliance and sparkle. Clarity factors in a variety of diamond attributes to assign its own grading standards to fancy shapes.
Selecting Cut Grade
Cut is often considered the most important of the 4 C's of diamonds (carat is more of a preference, not an art or science). When selecting a diamond, it is certainly important to ensure light is not lost. Excellent cuts are most premium and Very Good cuts offer more value. The differences in sparkle are quite subtle, but they are noticeable when compared side by side. We recommend maximizing on the Cut grade, if possible.
Fancy shapes have fewer restrictions because beauty is in the eye of the beholder. Still, you can often safely go a grade lower with non-round diamond shapes. Excellent cut fancy shapes are fairly rare.
In the end, it's your decision and you must remember there are plenty of other factors that influence a diamond. You must choose which factors/attributes matter most to you.
Parts of a Diamond
The anatomy of a diamond consists of several parts engineered in precise locations to maximize diamond brilliance. The diamond's cut grade is actually determined by examining these parts in conjunction because one part can be perfect and another flawed. In order to have an excellent cut diamond, all the aspects of the diamond must be cut in the ideal way. Here are the parts that make up a diamond:
Table
The diamond table is the largest and top-most facet of a gemstone in which light penetrates and escapes with sparkle and fire. The ideal range for the table facet in a round cut diamond is between 54% and 61%. A larger table can make a diamond look larger because the reflection (not refraction) may be greater.
Depth
The diamond's depth is the distance from the table to the culet. Along with table, depth is a critical attribute in determining a diamond's cut grade. Diamonds that are cut too deep (larger distance from table to culet) will result in light leakage. Deeper diamonds will also look visually smaller than other diamonds that may possess the same carat weight. Diamonds that are cut too shallow (shorter distance from table to culet) will also result in light leakage and may lack sparkle. The ideal range for a round cut diamond's depth is between 59% - 62.9%.
Crown
A diamond's crown is the top part of the diamond above the girdle. It is called the crown because it is at the height of the diamond and from a profile view, it resembles an upside-down crown. The crown is where the maximum amount of light enters and escapes. The crown must be angled appropriately in order to bounce and reflect/refract light for maximum diamond sparkle and brilliance. A shallow crown or crown angle can look like a flat top, increasing light leakage. A heavy or steep crown angle can reduce light penetration and decrease the diamond's sparkle. The ideal crown angle for a round diamond is between 32.5 - 35 degrees.
Pavilion
The diamond pavilion is the bottom part of the diamond below the girdle. Like the crown, the diamond's pavilion must be correctly faceted and angled in order to refract light. Once light enters the crown, it is the pavilion's job to bounce light back to the eye, creating a sparkle effect. If the pavilion angles are too deep or shallow, light will fall through, potentially reducing sparkle. The ideal pavilion angle for a round diamond is 40 - 41.6 degrees.
Girdle
The girdle of a diamond is the thinner center portion between the crown and pavilion. It is the widest point of a diamond. Girdles can be polished, faceted, or unpolished. Modern diamonds tend to have slightly thinner polished and faceted girdles. The thickness of a girdle can have great implications on the cut grade of a diamond. The ideal girdle range is thin to slightly thick. Very thin girdles can chip or break during the setting process, and very thick girdles can create girdle reflections within the diamond, thereby reducing the diamond's sparkle.
Culet
The culet of a diamond is the bottom-most point of the diamond. It seals the diamond to prevent light from falling through, ensuring it bounces around inside for sparkle. Most diamonds have a point culet graded None. Medium or large culets can leak light, seen in old mine or old European cut diamonds. The culet is delicate and can chip from blunt impact or trauma.
Diamond Brilliance: What Makes Sparkle
Understanding diamond brilliance and fire: The process of transforming rough diamonds into sparkling gems involves removing their opaque exterior. Key factors like refractive index and dispersive power determine a diamond's brilliance and fire. Brilliance results from light reflections within the diamond, influenced by angles and faceting. Fire, the spectral separation of light, adds color flashes. Optimal brilliance and fire depend on precise proportions, including crown and pavilion angles, culet size, and total depth. For maximum sparkle, consider diamonds with steeper crowns and smaller table facets.
Diamond Cut History
Evolution of diamond cutting: From rough to polished, diamonds have transformed significantly over time. Early cuts like the point cut in the 14th century gave way to the rose or antique cut, characterized by large facets. Modern diamond cutting, pioneered in the 1900s by Tolkowsky, focused on proportions for brilliance. Today, machine cutting ensures precision, but variations in cut grades reflect diamond nature and cutter priorities."
If there's anything else you'd like to know or discuss, feel free to ask!
The Diamond's True Size or 'Spread'
Spread, or a diamond's measurements, is straightforward for buyers to understand. Diamonds with greater spread (less total depth) appear larger. Despite this, many cut grading systems do not consider spread, which contrasts with its simplicity in evaluation. While larger-looking diamonds aren't necessarily more sparkly, they're often more desirable with a premium. Two diamonds of the same carat weight can differ in spread, not weight. Opting for diamonds in the excellent cut range with maximum measurements can offer both sparkle and size, albeit at a slight premium.
Expert Buying Tips
Try to maximize on the cut score and grade of the diamond. This represents the sparkle of the diamond and can help mask (or make up for) lower clarity grades, color tints, or smaller than desired carat weights. You may find value in a 'Very Good' cut diamond that has most of the technical aspects of an Excellent cut diamond but missed the cutoff due to a technicality such as a thick girdle or larger table facet.