The Diamond Cuts Guide
Understanding the most important of the diamonds 4 Cs
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Cut is possibly the most important of the 4Cs. If you ignore it, you can make an enormous mistake. For example, this diamond from James Allen seems like a great find, as it is 6% cheaper than this diamond from James Allen. In reality, the diamond will have no brilliance and is very poor value.
Here’s what we’ll cover in this article:
What is a diamond cut?
What is the best diamond cut?
What proportions of the diamond cut are important?
What are the prices for different diamond cuts?
Is there a difference between diamond cut and diamond shape?
Bottom line recommendations when looking at diamond cut
What is a “Diamond Cut”?
Diamond Cut is how well a diamond is cut and polished, including how well-proportioned the stone is, its depth and symmetry. You may sometimes encounter someone referring to a diamond shape as cut, as in princess cut diamond, radiant cut diamond, or emerald cut diamond, but diamond cut doesn’t refer to the shape of the diamond at all. Cut quality directly impacts the diamond’s beauty and brilliance. A well-cut diamond is luminous and reflects white and colored light back to your eyes. A poorly cut diamond is dull instead of brilliant.
Differences in cut greatly impact beauty, aesthetic appeal and the value of a diamond. It is the most important of the 4Cs.
What are GIA Cut Grades?
In August 2005 the GIA announced the introduction of a new “cut grade” to its grading reports. According to JCK Online Magazine “The addition of a cut grade to the GIA Diamond Grading Report and GIA Diamond Dossier for round brilliant diamonds is the result of more than 15 years of research and testing, including sophisticated computer modeling and ray tracing of more than 38.5 million proportion sets.”
GIA diamond cutting grades for a round brilliant cut diamond will range from Excellent to Poor. Diamond cut grade is based on a number of factors including symmetry, polish, brilliance and fire. For the most brilliance and beauty, only consider Round Brilliant cut diamonds with an Excellent cut. Ensure the symmetry and polish of the diamond are either Excellent or Very Good.
The reality is that 55% of all Round cut diamonds receive an excellent cut grade from the GIA. About 25-30% of these “excellent” cut diamonds are not recommended. Our consultants review thousands of Excellent cut diamonds and find bad specs (depth, table, and angles).
That’s why it’s important to look at the cut grade of a diamond on the GIA certificate, but to also review the diamond closely yourself or ask an expert. You don’t want to end up paying for an Excellent cut diamond that’s only mediocre.
Diamond Cut Grade Chart
A professional gemologist at the GIA reviews each diamond under magnification to determine the Cut grade. Here are the GIA cut grades for round diamonds:
| Excellent | Excellent Cut Diamonds provide the highest level of fire and brilliance. Because almost all of the incoming light is reflected through the table, the diamond radiates with magnificent sparkle. |
| Very Good | Very Good Cut Diamonds offer exceptional brilliance and fire. A large majority of the entering light reflects through the diamond’s table. To the naked eye, Very Good cut diamonds provide similar sparkle to those of Excellent grade. |
| Good | Good Cut Diamonds showcase brilliance and sparkle, with much of the light reflecting through the table to the viewer’s eye. These diamonds provide beauty at a lower price point. |
| Fair | Fair Cut Diamonds offer little brilliance, as light easily exits through the bottom and sides of the diamond. Diamonds of a Fair Cut may be a satisfactory choice for smaller carats and those acting as side stones. |
| Poor | Poor Cut Diamonds yield nearly no sparkle, brilliance or fire. Entering light escapes from the sides and bottom of the diamond. |
The AGS cut grade chart also includes an Ideal grade. Cut quality is graded by the AGS as Ideal, Excellent, Very Good, Good, Fair or Poor. When looking at AGS diamonds, we recommend only considering Ideal cut diamonds for the best quality.
How to Choose the Best Diamond Cuts
With most of the 4 C’s of diamonds (the others being Clarity, Color and Carat weight), there’s a sweet spot where beauty and value meet up.
To use diamond clarity as an example, there is a point (generally around VS1-VS2) where any increase in grade is not going to offer a noticeable increase in beauty. To the naked eye, a VS1 or VS2 diamond will likely appear clean and flawless.
Diamond Cut, however, is different. It’s the one grade you don’t want to compromise on. While middling grades in clarity or color can be concealed, and low-carat diamonds can still have a radiant and beautiful appearance, a low cut grade is likely to result in a diamond that doesn’t dazzle like it is supposed to.
We recommend you restrict your search to only Excellent or Ideal cut grades, as there is no hiding a below-average cut. Even if your budget forces you to sacrifice in other areas, a well-cut diamond should still have the potential to stand out.
Prices for Different Diamond Cuts
As with all areas in which diamonds are graded, the price can rise and fall a lot depending on your choice of cut grade.
Their prices are based on the precision and quality of the cut—primarily its proportions and symmetry. For example, this diamond from Blue Nile is about as perfect a cut as you can get. The depth, table and all other proportions are as exact as can be. Because of that, you are paying a higher price for the diamond, even compared to a typical excellent cut diamond.
If the diamond’s facets (the glossy flat surfaces of a diamond) are proportional, for instance, they refract and reflect light back to the eye in tremendous fashion. Diamonds that aren’t as precisely cut have facets and pavilions that do not refract and reflect light as spectacularly.
The amount of light return and brilliance found in an exceptionally cut diamond is worth the extra price. Without brilliance and fire, a diamond is less than radiant—no matter the Carat weight or table size.
In other words, a diamond’s Cut is the quality that most significantly impacts its beauty. That’s why the higher diamond cut prices are worth every penny—and it’s better to spend more on Cut than on Color or Clarity.
If you’re working within a budget, we recommend forgoing a GIA grade in Color and Clarity to ensure you’re selecting an ideal cut diamond.
What is Ringo?
Factors that Affect a Diamond’s Cut
The most important factor in a diamond’s value and price is its Cut quality. Many elements are involved in Cut quality including its proportions, facets, finishing details and ability to reflect light. The better these characteristics are as a whole, the higher the quality of the diamond, and in return, the higher the price. While Color and Clarity play a role in a diamond’s beauty, Cut is the most critical of the 4Cs.
Here are the main factors that affect the price of a diamond:
- Proportions (table, width, depth)
- Symmetrical diamond’s facets (the mirrors, windows and steps of a diamond)
- Brilliance (brightness of white light reflection)
- Fire (dispersion of colored light)
- Scintillation (the flashes of sparkle when light moves)
- Finishing details (permanent treatment and polishing)
Diamond Cut Proportions
To further understand the factors impacting Diamond Cut quality, let’s examine a diamond’s proportions, primarily its table, width and depth. These elements are universally measured and are excellent indicators of a diamond’s cut quality.
Diamond Cut Proportions directly affect a diamond’s ability to reflect light and provide brilliance. Proportions are based on the ratios between size, angle and shape of each diamond facet. Various combinations of these elements impact how the diamond will interact with light, which determines its overall beauty and lasting appeal (as well as its GIA grading). Don’t forget that different diamond shapes have different proportions.
Diamond Table
Diamond table % is determined by dividing the width of the table (top surface area) by the width (diameter) of the diamond. For example, if the table facet is 3.5mm wide, and the diamond is 5mm wide, the table % is 70%.
If the table percentage is too large, light won’t reflect off of the diamond’s crown angles and facets. Vibrant reflections of color won’t be seen as the light will escape from the top of the diamond instead of reaching the eye.
If the table percentage is too low, light will remain trapped inside the diamond and be emitted through other parts of the diamond instead of to the eye.
The ideal table % depends heavily on the Diamond Shape. If you’re unsure of an excellent table % for your diamond, please contact us and we will walk you through the options and factors.
Diamond Width
A diamond’s width is determined by measuring from one end of its girdle (the diameter at its widest point) to the other end of the girdle.
The width is most important when it comes to determining length to width ratio, which signifies how proportionate the diamond is along with its intended shape (i.e. square vs. rectangular).
Length to width ratio is measured by dividing the length of the diamond by the width. For example, if a diamond has a length of 5mm and a width of 3mm, the length to width ratio is 1.67.
Diamond Depth
Depth % refers to the height of the diamond, from the culet to the top of the table. Depth is measured in millimeters and percentage. By dividing the depth by the width, the depth % is achieved.
As an example, if a diamond is 4mm in depth and 4.5 mm in width, the depth percentage is 88.8%.
In most cases, a lower depth % of two equal carat diamonds will appear larger due to the increased width. On the other hand, a depth % that is too low can create a darker appearance as it will not reflect light as powerfully.
Shallow Diamond Cut
When a diamond is cut is too shallow, light hits the pavilion at a low angle. The light travels through the diamond and exits through the sides, instead of reflecting through the table and to your eyes.
While shallow cut diamonds may seem large based on their table size (they are also called Spready Diamonds), the escape of light at the bottom significantly reduces the diamond’s brilliance, sparkle and fire.
Deep Diamond Cut
When a diamond is cut too deep, light hits the pavilion at a sharper angle, causing it to immediately reflect to another pavilion. The light is forced to retract and pass through the bottom of the diamond. As this happens, light is dulled and the diamond becomes less vibrant and radiant.
A deeply cut diamond also tends to look smaller than those of an ideal cut.
What is the best Diamond Cut?
Simply put, a well-cut diamond maximizes the light that strikes each pavilion. Instead of escaping through other parts of the diamond, light reflects back through the crown and table. For our readers that are focused on cut, they have had the most success with James Allen’s True Hearts and Blue Nile’s Astor Cut diamonds.
When it comes to determining the highest grade possible, GIA uses the term “excellent” while AGS uses the word “ideal.” These cuts are well proportioned with optimal facet angles, allowing the brilliance and fire to pass through the table for all to see.
For these reasons, excellent cuts are more valuable and more luminous. When buyers have a budget, we often advise choosing a smaller, well-cut diamond as opposed to a larger carat that is poorly cut to get the most sparkly diamond.
If you’re unsure of an ideal cut for your diamond, speak to an expert to walk you through the process.
Symmetrical facets
The facets of a diamond are the tiny mirrors that reflect light back to your eyes. Facets surround the diamond’s table. There are facets above the girdle and below the girdle. The pavilion (the part of the diamond below the girdle that reaches to the culet) is also made up of facets. Round Brilliant cut diamonds have 58 facets total.
The size, placement and symmetry of the facets impact how well the diamond refracts and reflects light. A diamond with unproportioned facets, too many facets or fewer facets, can cause a less than ideal diamond.
Brilliance
A diamond’s brilliance is the brightness of the white light reflection. When looking at a diamond face-up under light, it should reflect an abundance of white light. A diamond that’s not symmetrical, is cut too deep or too shallow, for example, looks dull instead of brilliant.
Fire
A diamond’s fire is the amount of colored light that reflects off of the table and facets. Well-cut diamonds not only have brilliance but fire too. When looking at the diamond face-up under light—especially daylight—you should see colored light bouncing off of the diamond. If the diamond doesn’t exhibit colored light reflection, the diamond has a low amount of fire.
Scintillation
Scintillation of a diamond refers to the flashes of sparkle when light moves on the diamond’s table and facets. The scattering of light resembles a sparkle and is caused by the light and dark areas on the diamond’s surface. A diamond with a large amount of scintillation is more desirable. A diamond without much scintillation can appear dull.
Finishing details
The finishing details are the craftsmanship of the diamond and include its permanent treatment and polishing. The polish of a diamond refers to the condition and quality of the facet surfaces. A diamond that is polished well creates a clear mirror for light to reflect off of. A diamond with a poor polish job looks dull because the facets don’t reflect light as vividly.
Factors for Determining Diamond Cut Quality
Because Diamond Cut is an enormous element in determining the beauty and brilliance of any diamond, there are some complexities. Many factors play a role in how a diamond’s cut quality is determined.
The main factors impacting Diamond Cut Quality are:
- Proportions: the ratios and sizes of the diamond’s depth, width and table
- Symmetry: precision of the facets, mirrors, windows and steps
- Polish: the shine and glow of the diamond surface
When you’re looking to see how well-cut diamonds are, take note of how their facets and angles reflect light. Specifically, note how bright and sparkly the light return is when placed under a normal lamp.
You’ll want to gauge diamonds’ fire (the rainbow light of reflection) and brilliance (colorless light and sparkle of the diamond). Be sure to also watch for any dark spots within the piece.
When a diamond is poorly cut (even if it has a high Color or Clarity grade), light will not reflect as well back to your eyes, making it a duller, more lifeless diamond.
Be sure to review the GIA cut grade on a diamond’s report, which will include ratings of Poor, Good, Very Good or Excellent.
What’s the difference between Diamond Cut and Diamond Shape?
The terms diamond cut and diamond shapes have distinct meanings.
Diamond Shape describes the outline or figure of the diamond. For example, Pear, Oval and Round Brilliant refer to the shape appearance of the diamond.
Cut refers to the facets, symmetry, dimensions and reflective qualities of the diamond. Pear shaped diamonds, for instance, may be cut shallow or deep, dull or brilliant. The Heart Shape remains, while the Cut may differ significantly. The finer the cut, the greater the brilliance and fire of the diamond.
Bottom Line Recommendation:
The difference between a well cut diamond and a poorly cut diamond is enormous. You can have something like this ridiculously brilliant diamond from James Allen that runs circles around a poor cut like this one from James Allen.
To come away with a beautiful, brilliant diamond, cut quality has to be a priority. Read on to learn all you need to know about the perfect diamond cut.
What to Look for
What to Avoid
For the most brilliance and beauty look for a round diamond
Don’t sacrifice on diamond cut in order to save money as you might end up with an underwhelming diamond.
For a Round Brilliant diamond, consider only GIA Excellent or AGS Ideal cut grades.
Don’t consider buying a diamond that doesn’t carry a certificate from a reputable entity like the GIA or AGS.
For fancy shaped diamonds, it’s essential that you see a high quality image of the diamond before you buy.
Stay away from diamonds that are too deep or too shallow. They won't refract the light properly.
Focus on diamonds that display symmetry, even proportions, and have few dark spots.
Having trouble navigating the diamond buying minefield? We are happy to help. CONTACT US
More Questions on Buying the Right Diamond Cuts? Contact Us
When it comes to selecting an ideal diamond for engagement rings, we recommend a quality diamond cut over anything else. For GIA Certified Diamonds, we recommend choosing an Excellent cut grade. For AGS Certified Diamonds, choose an Ideal cut. When we search for a diamond, we filter more heavily on cut. You can see our parameters by looking at a James Allen diamond search.
For Maximum Brilliance: Consider a Brian Gavin Signature cut. Brian is a leading industry expert in the field of cut optimization. His Signature cuts are on par with the famed Hearts on Fire brand—only far cheaper.
For Round Brilliant Cut Diamonds, don’t give any credence to an online vendor’s cut grade. Only focus on the GIA or AGS cut grade on the certificate.
In addition to reviewing a GIA or other grading report, be sure to look at the diamond yourself or have an expert assist you. Most importantly, ensure the diamond is appealing to you and your personal style and desires.
Our primary focus is making sure your diamond search is easy, simple and accurate. We want you to find the highest quality diamond while staying within your budget.
If you’d like assistance with finding and selecting a diamond, we’ll be happy to filter through the cuts and make recommendations for you.
What we love about them:
- No questions asked returns within 30 days of shipment. James Allen will send you a paid shipping label to return the ring.
- Lifetime Warranty
- Free International Shipping
- Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
- Provide insurance appraisals
- One free resizing within 60 days of purchase
- Free ring inscriptions
- Best-in-class high quality imagery of all diamonds in stock
- 24/7 Customer Service
- Best-in-class packaging
What we love about them:
- No questions asked returns within 30 days of shipment. Blue Nile will send you a paid shipping label to return the ring.
- Lifetime Warranty
- Free Shipping
- Free prong tightening, repolishing, rhodium plating and cleaning every 6 months
- Provide insurance appraisal
- One free resizing within the first year of purchase
- High quality images of about half of their diamonds
- 24/7 Customer Service
- 100% credit towards future upgrades (must be at least double in value)
- Best in class fulfillment
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