Diamond Cut: The Complete Guide

diamond cut grade

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As some might assume the cut grade refers to the diamond’s shape (round, princess, cushion, pear) this grade refers to the dimensions and angles of the diamond and assesses how well-proportioned a diamond is and how well it interacts with light. Further more, an ideal cut diamond has more brightness, fire, and scintillation compared to a lower cut-graded diamond.

The common view among diamond experts is that cut is the most important aspect of the 4C’s, as most people want to get a stone that shows brilliance and fire. To know if the diamond is well cut, we need to look for a specific range of dimensions, ratio (in percentages) between certain dimensions and angles of the diamond, and this is when things are getting more complicated.

My goal is to simplify things so you won’t get lost with all those numbers.

Table of Contents

Diamond cut proportions

The main factor that influences the diamond’s brilliance and how it interacts with light is the cut proportions. When we look at a diamond ring, most of the time we view the diamond from the top. Ideal proportions reflect light directly into our eyes through the diamond’s table, which is exactly what we want.

Lower cut grades have too deep or too shallow proportions. These proportions move the light into “wrong” directions, so it exits through the side or bottom of the diamond and loses the brilliance, fire, and shine.

Diamond cut quality

There are 3 main factors that have an impact over the diamond cut quality:

  • Proportions: The ratios and sizes of the diamond’s depth, width, and table.
  • Symmetry: The precision of a finished diamond’s shape and facet placements.
  • Polish: The overall degree of smoothness of each facet of a diamond and how it affects the shine and flow.

The GIA diamond Cut grading system

Most of the diamonds industry follows a cut scaling system that was created by the GIA (Gemological Institute of America, a non-profit organization) which rates the diamond’s cut with the following grades (from best to worst):

  1. Excellent (Ideal cut)
  2. Very-Good
  3. Good
  4. Fair
  5. Poor

When most diamond experts will give you specific rations and measurements to look for, I’m telling you…

For round shape diamonds, save your time, don’t compromise and look for the triple ex: Ideal cut, excellent polish, an excellent symmetry, and most importantly – see the diamond for yourself and make sure it looks beautiful. By using JamesAllen’s 360HD and the Super-Zoom feature, you will see the total appearance of the diamond and decide if you like it or not. If you know it looks beautiful on the 360HD and Super-Zoom, it will look beautiful on her engagement ring.

Fancy shape diamonds cut

Unlike round brilliant diamonds, for fancy shape diamonds (cushion, pear, heart and more…) there isn’t such a thing as “right” or “wrong” proportions as it’s a matter of taste. For example, some might like a longer pear while some prefer it shorter. It also depends on the type of jewelry: a fancy shape with a specific length and width ratio can be beautiful on a necklace, while a different ratio looks better on a ring.

Yet, I recommend looking for: cut, symmetry & polish which are graded as very-good or excellent. Again, most importantly – make sure the diamond looks great by using the Super Zoom feature.

The best diamond cut of them all: hearts and arrows

The best of the best is “Hearts and Arrows“ diamonds. These diamonds are a tiny subgroup, less than 1% of the excellent/ideal cut diamonds. What makes them special is that due to extremely precise symmetry and specific proportions, these diamonds display 8 perfectly symmetrical arrows from a top view and 8 perfect hearts from bottom view (pavilion view). These unique characteristics are very hard to achieve even for the most skilled diamond cutter in the diamond industry.

There is a unique technology that generates red and white “Ideal Scope” images to show a clear image of the hearts and arrows effect. Some stores might claim they sell Hearts & Arrows – You should ask them to show you these images so you can verify that his is true.

JamesAllen has Hearts & Arrows round diamonds, as part of their premium True Hearts brand. They display the ideal scope images on the diamond item-page. Many consider the 9 hearts and the 9 arrows as a symbol for their infinite love. For that, you really need perfect hearts and perfect arrows. It is very difficult to find such diamonds elsewhere.

8 arrows from table view

8 hearts from table view

The True Hearts brand includes also Princess and Cushion shapes which are graded as Ideal by the AGS lab for all attributes: cut, polish, symmetry and most importantly light performance.

How Diamond Cut effect price

It is more expensive to polish a better cut diamond for two reasons. For once, we need a more skilled polisher, who naturally deserves and gets higher pay. The second and more significant reason is that when polishing a diamond to ideal measurements, angles, and proportions, you end up with a smaller diamond. For example, if we polished a rough diamond to a 1 carat, which is too deep or too shallow, and we wanted to turn it into an ideal cut, its weight would decrease to only 0.90 carat or even less than that. If you compromise on the cut and buy such a 1 carat, you should pay no more than the price of the 0.90 ideal cut. A different way to look at it is that for a 1 carat ideal cut diamond we would have needed to begin with a larger rough diamond, which costs much more.

In conclusion, you should never comprimise on the diamonds cut and aim for Ideal cut. Above all, this factor as the most influence over the brilliance of the stone which adds the WOW factor. Moreover, if I needed to purchase 1 carat diamond with a limited budget, I would compromise on clarity and color. I personally will go for a lab-created diamond, where I can get higher color, better clarity and a larger size for my budget.

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My recommended online retailers

Online retailers offer much better prices due to lower business expenses. Unlike your local jewelry store, they have a huge inventory (600,000+ diamonds), so we can find the best one for you. Inspecting a diamond is much easier as well. We can check each stone with a 360HD video that shows it under 20-40X magnification.

Author: Yaniv Hadar

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