Ideal Proportions

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Ideal Cuts

Crown
 angle and pavilion depth play a significant role in picking a super ideal cut diamond from an ideal cut diamond. These two factors can help distinguish two round cut diamonds with equally excellent cut, symmetry, and polish grades from GIA. These proportions also apply
 to&nbsp;<a href="https://www.petragems.com/education/lab-grown-diamonds/">lab-created diamonds</a>.Evaluate these proportions with these 40X Diamond <a href="https://www.jamesallen.com/loose-diamonds/all-diamonds/?a_aid=5c83f22427304/" class="external" rel="nofollow">Magnified Videos</a>. <table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="780" style="width: 97.6929%; margin-left: 0.318218%;">
 <tbody>
 <tr>
 <td valign="top">
 Cut
 </td>
 <td valign="top">
 Depth%
 </td>
 <td valign="top">
 Table%
 </td>
 <td valign="top">
 Crown Angle
 </td>
 <td valign="top" style="width: 13.3929%;">
 Pavilion Angle
 </td>
 <td valign="top" style="width: 21.4286%;">
 Girdle
 </td>
 </tr>
 <tr>
 <td valign="top">
 Super Ideal Round Cut
 </td>
 <td valign="top">
 60-62.1%
 </td>
 <td valign="top">
 54-58%
 </td>
 <td valign="top">
 33.9-34.9
 </td>
 <td valign="top">
 40.2-41
 </td>
 <td valign="top">
 Thin - Slightly Thick (2-3.5%)
 </td>
 </tr>
 <tr>
 <td valign="top">
 Ideal Round Cut
 </td>
 <td valign="top">
 59-62.8%
 </td>
 <td valign="top">
 53-59%
 </td>
 <td valign="top">
 33.9-35.5
 </td>
 <td valign="top">
 40-42
 </td>
 <td valign="top">
 Thin - Slightly Thick (1.5-4%)
 </td>
 </tr>
 </tbody></table> Polish VG to Excellent for Ideal and
 Excellent for Super IdealSymmetry VG to Excellent for Ideal and
 Excellent for Super Ideal

Round Super Ideal Cut Proportions

<table class="MsoNormalTable" border="0" cellspacing="0" cellpadding="0" width="780" style="width: 97.6929%; margin-left: 0.318218%;">
 <tbody>
 <tr>
 <td valign="top">
 Cut
 <div style="color:rgba(0,0,0,0.01);width:0;height:0">&nbsp; </div></td>
 <td valign="top">
 Depth%
 </td>
 <td valign="top">
 Table%
 </td>
 <td valign="top">
 Girdle
 </td>
 <td valign="top" style="width: 16.7208%;">
 Culet
 </td>
 <td valign="top" style="width: 17.776%;">
 Length to Width Ratio
 </td>
 </tr>
 <tr>
 <td rowspan="2" valign="top">
 Ideal Princess Cut
 </td>
 <td rowspan="2" valign="top">
 64-73
 </td>
 <td rowspan="2" valign="top">
 62-69
 </td>
 <td rowspan="2" valign="top">
 Thin-Slightly Thick
 </td>
 <td rowspan="2" valign="top">
 None to Very Small
 </td>
 <td valign="top">
 Square: 1.00-1.05
 </td>
 </tr>
 <tr>
 <td valign="top">
 Rectangular: 1.49 -1.73
 </td>
 </tr>
 <tr>
 <td valign="top">
 Ideal Oval Cut
 </td>
 <td valign="top">
 57-62
 </td>
 <td valign="top">
 53-64
 </td>
 <td valign="top">
 Thin - slightly thick
 </td>
 <td valign="top">
 None to Very Small
 </td>
 <td>1.4-1.55 </td>
 </tr>
 <tr>
 <td rowspan="2" valign="top">
 Ideal Radiant Cut
 </td>
 <td rowspan="2" valign="top">
 61-67
 </td>
 <td rowspan="2" valign="top">
 62-70
 </td>
 <td rowspan="2" valign="top">
 Thin - slightly thick
 </td>
 <td rowspan="2" valign="top">
 None to Very Small
 </td>
 <td valign="top">
 Square: 1.00-1.05
 </td>
 </tr>
 <tr>
 <td valign="top">
 Rectangular: 1.20 -1.31
 </td>
 </tr>
 <tr>
 <td rowspan="2" valign="top">
 Ideal Cushion Cut
 </td>
 <td rowspan="2" valign="top">
 61-67
 </td>
 <td rowspan="2" valign="top">
 61-68
 </td>
 <td rowspan="2" valign="top">
 Thin - slightly thick
 </td>
 <td rowspan="2" valign="top">
 None to Very Small
 </td>
 <td valign="top">
 Square: 1.00-1.05
 </td>
 </tr>
 <tr>
 <td valign="top">
 Rectangular: 1.2 -1.25
 </td>
 </tr>
 <tr>
 <td rowspan="2" valign="top">
 Ideal Emerald Cut
 </td>
 <td rowspan="2" valign="top">
 61 - 67
 </td>
 <td rowspan="2" valign="top">
 62-70
 </td>
 <td rowspan="2" valign="top">
 Thin - slightly thick
 </td>
 <td rowspan="2" valign="top">
 None to Very Small
 </td>
 <td valign="top">
 Square: 1.00-1.05
 </td>
 </tr>
 <tr>
 <td valign="top">
 Rectangular: 1.39 -1.50
 </td>
 </tr>
 <tr>
 <td valign="top">
 Ideal Asscher Cut
 </td>
 <td valign="top">
 61-67
 </td>
 <td valign="top">
 62-70
 </td>
 <td valign="top">
 Thin - slightly thick
 </td>
 <td valign="top">
 None to Very Small
 </td>
 <td>1.00-1.05 </td>
 </tr>
 <tr>
 <td valign="top">
 Ideal Marquise Cut
 </td>
 <td valign="top">
 57-62
 </td>
 <td valign="top">
 53-64
 </td>
 <td valign="top">
 Thin - slightly thick
 </td>
 <td valign="top">
 None to Very Small
 </td>
 <td>1.8-2.05 </td>
 </tr>
 </tbody>
</table>

Fancy Shape Ideal Cut Proportions

While the cut is undeniably essential, a diamond's brilliance is influenced by all four Cs—cut, color, clarity, and carat weight. Ideally, achieving super ideal cut proportions
without <a href="https://www.petragems.com/education/how-compromise-diamonds/">compromising the other 3Cs</a>&nbsp;is the best approach. However, while striking a balance between the 4Cs, prioritizing the cut grade is important.It is acceptable for the proportions to be slightly higher
or lower. According to GIA (Gemological Institute of America), we can model these proportions slightly differently and still achieve the same level
of brilliance. A 0.2-0.3% tolerance up or down from the super ideal proportions range is acceptable.Learn
 more about the&nbsp;<a href="https://www.petragems.com/education/is-diamond-cut-important/">importance&nbsp;of cut</a>&nbsp;among
 the 4Cs.<a href="https://www.petragems.com/round-cut-diamonds/"><img loading="lazy" class="img-responsive" src="https://backend.petragems.com/public/api/Images/img-1688238559.webp" alt="ideal cut diamond" width="618px" height="271px" title="ideal round cut" style="width: 618px; height: 271px;"></a>

Balancing Cut Within the 4Cs

Brilliance is hailed
 as the ultimate factor in determining the overall beauty of a diamond.

GIA refers to
 brilliance as "the intensity of the internal and external reflections of white
 light to the eye from a diamond or other gem in the face-up position" and
 measures it in terms of Weight Light Return (WLR).

After many studies and
 models, the industry has reached some consensus around the proportions of a diamond that will establish the quality of its cut. Cut plays an important role in determining a diamond's brilliance. For example, it might be helpful to check these proportions for a <a href="https://www.petragems.com/round-cut-diamonds/">round</a> or <a href="https://www.petragems.com/education/cushion-cut-diamonds/">cushion shaped</a> stone and see how they affect&nbsp;their cut.

The findings of&nbsp;<a href="https://www.google.com/url?sa=t&amp;rct=j&amp;q=&amp;esrc=s&amp;source=web&amp;cd=3&amp;cad=rja&amp;uact=8&amp;ved=0ahUKEwj3tbelpLfMAhXClIMKHYzSD80QFgg0MAI&amp;url=http%3A%2F%2Fwww.gia.edu%2Fcs%2FSatellite%3Fblobcol%3Dgfile%26blobheader%3Dapplication%252Fpdf%26blobheadername1%3DContent-Disposition%26blobheadername2%3DMDT-Type%26blobheadername3%3DContent-Type%26blobheadervalue1%3Dattachment%253B%2Bfilename%253DModeling-the-Appearance-of-the-Round-Brilliant-Cut-Diamond%253A-An-Analysis-of-Brilliance%26blobheadervalue2%3Dabinary%253B%2Bcharset%253DUTF-8%26blobheadervalue3%3Dapplication%252Funknown%26blobkey%3Did%26blobtable%3DGIA_DocumentFile%26blobwhere%3D1355958272946%26ssbinary%3Dtrue&amp;usg=AFQjCNHXdJ9S3yAIWt25SiocpdIDqEHKPw&amp;sig2=BJ9VJAwNVGJGbowQWJuI3A" target="_blank">GIA's study</a>&nbsp;are rather interesting. It indicates that while
 proportions, such as the ones developed by&nbsp;<a href="https://www.petragems.com/education/most-famous-diamond-cutters/">Marcel Tolkowsky</a>&nbsp;for
 an ideal cut diamond, are important, a diamond does not need to be within these rigid parameters to obtain an optimal level of brilliance. Put
 differently, it could be argued that there are many ways to proportion a
 diamond for maximum brilliance. These findings confirm the commonly held view
 among cutters that a diamond does not need a prescribed depth or table
 (among other factors) to look as brilliant as one that meets rigid parameters.
 Proportion can be modeled differently to achieve optimal brilliance.

The key takeaway from
 these findings is that while these parameters are essential, they can only take
 us so far. We should not mark diamonds that are not precisely within the
 proportions of one grading model as inferior without inspecting their visual
 appearance. In some cases, their visual appearance might surpass the
 brilliance of one with ideal proportions. The issues of
 fire and scintillation should also be considered while evaluating the overall
 brilliance of diamonds.

Our advice to shoppers is not to spend too much time on brilliance, as it is an advanced and confusing topic for regular consumers to grasp quickly. Instead, we recommend using the&nbsp;<a href="https://www.petragems.com/education/diamond-certification/">GIA or AGS grading</a>&nbsp;systems
 and trusting their assessment. Since GIA does not offer a cut grade for
 shapes other than round, follow our general&nbsp;<a href="https://www.petragems.com/diamond-buying-guide/">diamond guide</a>&nbsp;for each shape of a
 diamond to get a well-cut stone.<a href="https://www.petragems.com/education/famous-diamond-cuts-hearts-on-fire-hearts-and-arrows-etc/" target="_blank"><img loading="lazy" class="img-responsive" src="https://backend.petragems.com/public/api/Images/img-1688495785.webp" alt="Heart and Arrows in Round Cut" width="300px" title="Heart and Arrows"></a>

Achieving Ultimate Brilliance

In the late 1990s, the
 Gemological Institute of America (GIA) conducted a study of brilliance. The
 most important insight from the study was that the proportions of a diamond
 could be modeled differently to achieve the same level of optimal brilliance.

The term
 "brilliance" refers to a diamond's brightness, which is determined
 by the amount of light reflected from within. Here is how it works: light
 enters the diamond through the "table" or the top and
 moves through a spectrum of colors as it bounces off the mirror-like facets and
 runs across the interior. When the light leaves the diamond, it is reflected in
 the eye.

In their Diamond Dictionary, GIA defines brilliance as "the intensity of the
 internal and external reflections of white light to the eye from a diamond or
 other gem in the face-up position." Cutting facets ultimately create brilliance, typically performed with a faceting machine. The ideal facet
 cut will produce the highest brilliance possible from the stone. If
 an expert artisan cuts the facets, there will be no light loss when reflected in a diamond. The less light reflected from the eye, the lower the stone's brilliance. Light is lost when the angle of the facets
 shoots the light upward or downward, resulting in lower brilliance.

GIA's Look into Brilliance

The brilliance of a
 diamond is measured using the (WLR) Weighted Light Return. A WLR is a numerical
 evaluation obtained by tracing and weighing rays of light as they pass through
 the interior facets of a diamond. No two diamonds will be identical. GIA's
 standard lighting state simulates the average amount of daylight when diamonds
 are viewed. The analysis also considers how diamonds are moved when looked at and glared at, which could be incorrect as WLR.

The researchers at GIA determined that the relationship between brilliance and the three
 primary proportion parameters (pavilion angle, crown angle, and table size) is
 complicated. Ultimately, the combination of the factors and how they interact
 determines the brilliance - any change will affect it unpredictably.

Around the same time that GIA was looking into the brilliance of diamonds, a group of scientists from Moscow State University produced a study on diamond brilliance. The
 study, led by Yurri Shelemetiev and Sergey Sivovolenko, included a theoretic
 result involving light return and fire. Using a virtual model analysis, unlike GIA, they used a realistic lighting environment. The researchers emphasized
 that light return should not be equated with brilliance and that human
 physiology was also a factor in determining an individual stone's brilliance.
 The main reason behind this finding was that, depending on the individual's
 eyesight and the angle at which they are looking at the stone, their opinion
 about the brilliance of the diamond might change or defer.

How is Brilliance Determined?

GIA's study on measuring the brilliance of diamonds&nbsp;utilized a computer that simulated a
 three-dimensional model of a round, brilliant, flawless, colorless
 fifty-eight-facet diamond that was wholly symmetrical and had perfect polish.
 Once established, they added eight-cut and physical factors that affect how light interacts with a diamond, including:

<ul type="disc">
 <li class="MsoNormal">Table size</li>
 <li class="MsoNormal">Lower girdle length</li>
 <li class="MsoNormal">Cutlet size</li>
 <li class="MsoNormal">Star length</li>
 <li class="MsoNormal">Girdle thickness</li>
 <li class="MsoNormal">Girdle facets</li>
 <li class="MsoNormal">Crown angle</li>
 <li class="MsoNormal">Pavilion angle</li>
</ul>

<a href="https://www.petragems.com/education/diamond-depth-and-table/"><img loading="lazy" class="img-responsive" src="https://backend.petragems.com/public/api/Images/img-1690218137.webp" alt="ideal table and depth" width="567" height="240" title="diamond table and depth"></a> Through the computer
 simulation, GIA determined the individual factors of a diamond that result
 in its brilliance. Any diamond cut and physical characteristics can
 dramatically alter how much brilliance a diamond has.

As time passed, the
 demand that GIA provide cut grades rose. However, it refused, knowing that
 since so many variables go into the overall appearance of a diamond, one cut
 will not be better than another. Instead, it created 20,122 proportion
 combinations in its simulation, mixing crown angle, pavilion angle, and table
 size while keeping the extra five factors constant. In the simulation,
 brilliance was determined using the WLR.

The most astounding discovery from the simulation was that some of the most popular diamond cuts, including the American Ideal, produced the least brilliance from their diamonds. However, even with that result, GIA said that
 the findings should not be used as a brilliance grade for all diamonds since it
 is not just cut that affects the brilliance of a diamond.

GIA's Modeling by Computer

Diamonds have been
 used for various purposes throughout history. The first mention of diamonds in
 ancient texts was in a Sanskrit manuscript written between 320 and 296 by a minister in northern India. While diamonds have been used for millennia, the history of studying their brilliance is shorter.

Around the 13th
 century in Europe, diamonds became associated with monarchies and
 aristocracies, set against pearls and gold as accent pieces. As centuries passed, diamonds became more prominent features in jewelry for the wealthy, which
 was greatly due to the understanding of diamond faceting. When diamond faceting
 was developed, the jewelers of the time found that the brilliance and fire of
 the diamonds were greatly enhanced, making them more attractive to wear than
 ever before. In the 17th century, the diamond became the small staple gemstone
 in high-class jewelry. By the 18th century, they had also become the
 most sought-after large gemstones. This increase in interest would have happened to a different degree if the brilliance of diamonds had not been studied.
 Since the more brilliance a diamond has, the more it reflects light, royals
 wearing diamond pieces would sparkle, making them seem even more impressive
 than they would have been otherwise.

While the world's
 royalty tried to obtain diamonds throughout the centuries, it was only at the
 end of the 19th century that the role of diamonds faced a change. The first
 event that affected them was the discovery of immense diamond deposits in South
 Africa in the 1870s. This meant that diamonds could be procured much more
 efficiently than ever before, and you did not need to be royal to have one. The
 other big event was that, following the fall of Napoleon III of France, the
 French crown jewels were sold to <a href="https://www.petragems.com/tiffany-co-jewelry-review/">Tiffany &amp; Co.</a> of New York and taken to the
 United States. Under the electric and gas lighting that had been steadily
 increasing around New York at the time, the brilliance of the diamonds was able
 to show off to a level that had never been seen before.

As a result of Tiffany &amp; Co.'s discovery and presentation of the crown jewels, jewelers learned
 the importance of displaying diamonds with the ideal illumination to make the
 stones' brilliance stand out. Since where the light comes from will affect
 the look of a diamond's brilliance, fire, and sparkle, most jewelers display
 diamonds in bright spotlights. If the jeweler wants to present the diamond's
 brilliance to the highest degree, they may use fluorescent illumination.
 However, doing so may come at the cost of dulling the fire and sparkle of the
 diamond.

The History of Diamond Brilliance

The way a diamond is cut significantly influences its ability to emit optimal brilliance (white light), fire (color light), and scintillation (sparkle). To dete

Diamond Proportions: Excellent vs. Super Ideal Cut