Lieber & Solow Operating in the Diamond Industry Since 1927

When it comes to the anatomy of a diamond, there are a lot of important features that one must consider. The graders of these diamonds grade on their proportions. The better the proportions, the more valuable the diamond. So what are these proportions? The main factors are table size, crown angle, girdle thickness, pavilion angle, culet. All combining to create the beautiful diamond. Let’s take a look at an overview of these features.

The Table

The table is simply the largest facet on a diamond. Most of the light enters the stone here and bounces back to the viewer. In general, you want the table to be pretty big, otherwise the diamond will look small and boring. However, if it is too large, then the diamond may lack fire. So there is a give and take with this size and how it meshes with the other features. For the most part, diamonds should have a table size that is between 52% and 62% of the diamond width. Once you are in that range, the table size is then a matter of personal taste.

The Crown

The crown affects how much dispersion or fire the diamond shows. If you cut the crown angle shallow, then the diamond will have excellence brilliance, but no fire. If you cut the crown angle steep, then the diamond will have excellent fire, but little brilliance. Steep angles will also hide a lot of weight without making the diamond appear any bigger.

When the diamond is being cut, the angle the cutter selects depends on whether they are working with a longer or wide rough. In general, you want the crown angle to be between 31.5-36.5°. So when it comes down to it, the crown angle is a trade-off between brilliance and fire. For excellent symmetry, the diamond must have the same crown angles all around. If there are different angles, then the table will appear slanted.

The Girdle

The girdle is the thin belt that is around the widest part of the diamond, but it does not cover much surface area. With that said, it is still very important to the overall proportion of the diamond. If the girdle is cut too thin, then it becomes a knife-edge. Which means it will chip more easily. If it is cut too thick, then the diamond gains weight without looking any bigger. This happens due to the fact that the girdle wraps around the widest part of the diamond. And any increase in thickness increases the carat weight. Ideally, the girdle thickness is between 3 and 3.5% of the total depth percentage.

There are a few different types of girdles. These are bruted girdles, polished girdles, and faceted girdles. All that have different features. Learn more about girdles and their importance to the price points of natural industrial diamonds.

The Culet

The culet refers to a point or a small facet at the bottom of a diamond. When there is a faceted culet, it helps to prevent chipping and forming unattractive feathers. But not all diamonds have culets. So take special care of loose, unmounted diamonds without culets.

When it comes to graders, they classify culet sizes according to visibility. These classifications are:

  • None
  • Very Small
  • Small
  • Medium
  • Slightly Large
  • Large
  • Very Large
  • Extremely Large

You will need magnification to viewing small, very small, and medium. But you can see large and above with the naked eye. When it comes to the culet size of preference, you are looking at None to Small. Those are the ones that will get an Excellent cut grade. Medium typically gets a Very Good cut. And any culet larger than Medium will be reflected as an unattractive dot at the center of the table.

Depth Percentages for a Diamond

When it comes to the depth percentage of a diamond, there are two ways this gets looked at: Total Depth Percentage and Pavilion Depth Percentage.

The total depth percentage tells you if the diamond is over or under weight. The graders of the diamond will calculate it by dividing the average girdle diameter by the table to culet length of the diamond and multiplying it by 100. In general, you want the total depth percentage to be in the range of 57.5 to 63%. If the total depth percentage is under 55%, then it may have shallow crowns, shallow pavilions, thin girdles, or a combination of these factors. And if the total depth percentage is over 65%, then it may have steep crowns, steep pavilions, thick girdles, or a combo of those factors.

Then we get to the pavilion depth percentage. The pavilion reflects the table. When you look into the diamond, you will see a gray octagon, which is the table’s reflection in the pavilion. In general, the pavilion depth percentage should range from 41% to 48%. When the pavilions are shallower than 41%, it will make the reflection pattern smaller and fragmented. This makes for a messy looking diamond. When the pavilions are deeper than 48%, it will cause the stone to look too dark. And if it becomes deeper than 50%, the entire table will look dark, which called nail head.

The Polish

Lastly, we get to the polish of a diamond covers how carefully the cutter finishes the stone’s facets. The GIA rankings for polish are

  • Excellent
  • Very Good
  • Good
  • Fair
  • Poor

In many cases, stones will have transparent polish lines from the polishing process. For an Excellent polish grade, the lines cannot be too visual when magnified. But if there are numerous or white polish lines visible during this magnification, then the grade will be lower. It is worth noting that a stone’s polish is not an integral part of the stone. Of course you want it to be Excellent, but it is not very noticeable either way. And an expert re-polishing can easily remove most marks. But if the bad polish remains on the stone, then it will appear dim and hazy, which impacts the appeal.

Diamond Symmetry

The symmetry of a diamond is an integral part of the stone. The grader will assess whether or not the facets of the same type all have the same size, as well as the proper angles and alignment. When aspects do not align, it makes the diamond look more unattractive. Uneven crown angles are one way for this symmetry to be off. But every one of the aforementioned aspects need to be even, otherwise the symmetry and thus the grade will be lower.

Contact Lieber & Solow

Lieber & Solow has been operating in the diamond industry since 1927 and has become one of the world’s leading suppliers of natural industrial diamonds. We also supply a full line of materials to diamond tool manufacturers around the globe. We have generations of experience and extensive inventories stand behind our team of knowledgeable specialists, which makes us our go to supplier for all things industrial diamonds. Together with our international partners and agents we service you our customers one diamond at a time.

For more information about our full selection of natural industrial diamonds, please reach out today. We partner with DeBeers in order to bring our customers the best in the industry. The number for our office is 212-354-4060. When you call, we can provide you with the various price points you are looking for, as well as any other information you need.