Diamond Cut

how to buy a fancy shaped diamond

Don’t Confuse Shape With Cut

Consumers often confuse cut to be the same as a diamond’s shape. They aren’t the same thing and it doesn’t help that many jewelers use these 2 terms interchangeably.

Strictly speaking, shape refers to the outline a diamond has (e.g. heart and cushion) while cut refers to a combined aspect of a diamond’s proportions and finishing (symmetry/polish).

In my opinion, cut is the most important factor among the 4Cs as it determines the brilliance and beauty of the diamond. I recommend that you always place your emphasis on getting the best cut possible.

Why Cut is Always KING?

Cut itself can make a diamond look bigger, improve the face up color and mask inclusions. This means you get a free boost in the other aspects of the 3Cs (color, carat and clarity) just by having a better cut!

You see, a well cut diamond will have better proportions that doesn’t cause excessive carat weight to be hidden in its side profile. This makes the diamond appear the right size for its weight compared to another diamond that is cut deeply and faces up smaller.

Having an increased light return will make the diamond face up whiter since more light is reflected back into the eyes of the viewer. Lastly, well cut diamonds will display an intense scintillation and fire which can easily hide inclusions under its sparkle.

Simplified Diagram to Show How Light Transverses Through a Diamond

how the cut of the diamond affects light rays

Did you know that the amazing play of light displayed by a diamond is actually governed by the laws of physics? On a fundamental level, the amount of sparkle and scintillation is dependent on how the light rays are refracted and reflected within the diamond. This is why the precise positioning and alignment of each facet matters since the facets act like tiny mirrors to interact with light.

In a well cut stone, a large percentage of light that enters the diamond gets reflected back into the viewer’s eyes. This gives the diamond a bright looking appearance and enhances its luster.

With less ideal cut conditions, light is lost through the sides of the diamond instead of being reflected back into the viewer’s eyes. This translates to a less brilliant and darker appearance in the diamond.

Did you know White Flash and Brian Gavin Diamonds are two of the most well-known online vendors who specialize in ideal cut diamonds with optimal light performance?

Understanding Basic Cut Grading – A Quick Video From GIA

   

   

In a typical grading report for a round brilliant diamond, you can find a similar diagram like the example below. On this diagram, an averaged measurement for different parts of the diamond will be indicated.

diamond proportions with description and explaination

Depending on technical you want to be, you can actually analyze each of these parameters and study the correlations between them. That will be in a slightly more advanced stage I will go into later on. Now, I know most people get scared or turned off when they see a technical diagram like this.

The easy alternative would be to simply use the GIA/AGS cut grading as a filter to select round diamonds. Gemological labs like GIA or AGS take the proportion variations of a diamond into account when assigning a cut grade. If any particular aspect of the cut proportions is an issue, the diamond will be assigned with a lower cut grade accordingly.

That means even if you blindly go along with any GIA triple excellent diamond, it is very unlikely for you to end up with an ugly looking stone. However, if you want to select the cream of the crop among the GIA triple excellent stones, you will need to do some extra work in filtering your choices.

But first, I want to show you visual appearances of the various cut grades by using photographic examples. Head onto the next page and continue reading…

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38 Comments

  1. Zam-
    October 9, 2014 at 9:42 am

    Hi Paul,

    1. What is your comment on Lights Performance Certification; for example Gemex and Sarin? Isn’t it now important to evaluate best cut diamond in advance/modern ways?

    2. With advancing technology of diamond cutting, don’t you agree that diamonds with more facets are better compared to the traditional 57/58 facets? (with the assurance that the light performance is excellent, of course!)

  2. Paul Gian-
    October 9, 2014 at 2:13 pm

    1) Gemex is a sales tool for jewelers and the equipment is expensive to purchase. By the way, Gemex is not an advanced technology per se. It’s been around for some time now. In contrast, the ASET does a better role of discerning precision cutting better than the Gemex and is more useful when it comes to evaluating light return critically.

    The Sarin has been used in almost all major labs (it still is) during the grading process because of its accuracy and speed.

    2) It depends. A modified round diamond cut creates a different flavor to the stone’s appearance. Assuming that the light return of the diamond is excellent, then it boils down to personal preferences to decide if the cut is “better”.

    https://beyond4cs.com/shapes/round/solasfera-vs-star-129/

  3. Eric Lam-
    October 14, 2014 at 5:07 am

    Hi Paul, I found your website. Interesting read. Can’t help but to ask based on Zam’s comments. Is it better to purchase diamonds which has a light performance certificate or based on a diamond cut chart? What’s the difference between ideal vs excellent? And why some jewelers do not have light performance certificate on their listings?

    Many thanks!

  4. Paul Gian-
    October 14, 2014 at 8:47 am

    If light performance reports are readily made available, I would say yes. It does help to have as much information as possible when buying a diamond. Reports like Gemex are good to have but not mandatory. Also, you shouldn’t buy diamonds that only have a Gemex report without a proper grading document.

    It depends on how and what you define “light performance certificates” to be. If you are referring to AGS’s platinum diamond report (https://www.agslab.com/products-platinum-diamond-quality-document.php), it is a decision that jewelers make when sending diamonds for grading.

    If they know that the diamond will come back with an AGS0 and score well in the system, they will choose to send the report to AGS. If they know that the diamond won’t score a perfect AGS000, they will opt to send the diamond to GIA (to get a triple excellent rating) or other labs for grading. Basically, it’s a game jewelers play to get the most “marketable” report and to make the most money out of a diamond they have.

  5. Daniele-
    October 15, 2014 at 12:09 pm

    Hey there Paul,

    I am very confused at this point. Been researching like crazy on your website and other places as well for months. My sister has an engagement ring and it shines like crazy, more than any other ring I’ve seen. I checked out her GIA certificate and was shocked to see her for cut/polish/symmetry were only VG/VG/G and not triple EX. Also her HCA score was a 3.7 on the chart. From everything I have read, it is confusing to see her specifications vs. the actual diamond performance.

    It makes me think if you do not see the diamond in person, the specifications don’t reveal much. I can’t tell the differences between ideal vs excellent. I even compared an IF stone to an SI1 stones and could not tell the difference. What is the point of getting high quality stones on paper when a lower quality stones performs and looks pretty much the same?

  6. Paul Gian-
    October 15, 2014 at 12:47 pm

    Hi Daniele,

    You are right about the point on comparing SI1 against IF diamonds. Clarity is not the major factor that influences how a diamond sparkles in real life. Cut is. I understand that it is easy to get confused especially when it comes to discerning optical performance critically.

    I was probably like you when I first bought my diamond ring. However, once you look at enough diamonds under various lighting conditions, you will start to see the differences between a “very good” cut diamond against a “ideal” cut diamond.

    This video clearly explains such differences in optics: https://www.youtube.com/watch?v=QJh5SH5fg3I

    Note that “very good” cut diamonds will still sparkle under spot lighting. That’s why many people often buy a “very good” or “good” cut diamond in a jewelry store that looks full of life because they are ‘cheaper’. However, once they take it out into normal everyday environments where diffuse lighting is dominant, they will start to notice a huge difference in the way the ring looks.

    For lay people, viewing diamonds in diffused lighting is the best way for your eyes to tell differences in cut quality. If you have time, look around your local stores and do more side-by-side comparisons.

    Paul

  7. Chris Ndlovu-
    November 9, 2014 at 3:29 pm

    Hi Paul,
    I want to set up a turnkey system to help a major diamond producing customer set up a lab and diamond evaluation system. I want to build a system where the customer should have enough in house equipment lab to sell different cut types to international buyers. I want to setup labs that you find in Erntweb, Surat, Dubai etc. These are diamond selling centers, I want to set up a similar smaller system. Please help me how to integrate a similar system. Thanks—

  8. Paul Gian-
    November 10, 2014 at 1:30 am

    Hi Chris,

    Unfortunately, that is beyond the scope of Beyond4cs.com. I could direct you to the more appropriate channels though.

    You might want to head over to the following URLs:
    http://www.gemologyonline.com/Forum/phpBB2/index.php
    https://www.idexonline.com/index.asp Check out the business forums and community talk.

    There are professional jewelers, diamond buyers/sellers and gemologists who can give you better advice in setting up such a system.

    Paul

  9. CC-
    October 12, 2015 at 4:37 am

    I used to say I hated diamonds, but recently I visited a museum and saw some jewellery made during the Napoleonic wars. All I can say is WOW – the diamonds looked soft and rich and definitely NOT overly/annoyingly sparkly. I’m told the cut was an “old miner’s cut”. Does this cut still exist? Are there equivalent modern cuts, for someone who wants less sparkle than the typical modern diamond?

  10. Paul Gian-
    October 12, 2015 at 5:35 am

    The Old Miner’s cut still exist in the modern day. In fact, some jewelers have reinvested lots of time and research to develop the cutting style into a “better” version of it today. You can read more details about them here: https://beyond4cs.com/shapes/cushion/old-mine-cut/

  11. CC-
    October 12, 2015 at 12:32 pm

    Thanks for the quick response! I’ll check it out!

  12. Michael-
    October 24, 2015 at 6:54 am

    Is there a visual difference between a diamond cut rating from AGL 0 (ideal) to an AGL 1 (excellent). In know that might not seem like a lot but the pictures I seen it kind of looks like it. Both those diamonds were on James Allen listed in the true hearts section. The only difference is the one with the AGL1 rating was a VVS1 with a pin point and the AGL 0 was a VS1 but had a feather towards the corner of the stone which is a princes cut. Both diamonds were around the same price. Any ideas? Thank you.

  13. Paul Gian-
    October 25, 2015 at 3:08 pm

    Yes. There would be a visual difference even between 2 AGS 000 diamonds. This can be attribute to the scintillation patterns as well as the kind of sparkle it gives off. (i.e. facet structure will create varying performances as well). It would be best to contact me via email with the 2 links you mentioned at James Allen. That would give me a better idea of how the diamonds look like in real life.

  14. Mark-
    April 18, 2016 at 7:08 pm

    Hi Paul,

    Thanks for putting this site together and pouring out your insight for us newly initiated into the diamond buying field.

    I’ve had it drilled into my head now, from you and other credible sources that diamond cut should be the top consideration when diamond shopping in order to maximize value. The problem is that I’m looking for a cushion cut diamond. When I visit sites like James Allen, they don’t allow you to sort diamonds buy cut grade. I had a representative at white flash explain to me that they don’t give cut grades to “fancy shapes”. What gives? Is there some other metric that I can use to determine whether a cushion shaped diamond is cut ideally?

  15. Paul Gian-
    April 19, 2016 at 3:13 am

    Use an ASET image to determine light performance: https://beyond4cs.com/2014/12/aset-reference-charts/

  16. John-
    July 5, 2016 at 9:08 pm

    Would there be any reason to go with one of these diamonds over another? All seem to be within your ideal cut specs. Are they a good value, or should i do more work to find value in something that might not be listed as “a cut above”?

    http://www.whiteflash.com/loose-diamonds/compare.aspx?idnos=3682323,3685711,3685701,3664949

    Thank you!

  17. Paul Gian-
    July 6, 2016 at 3:53 am

    All 4 stones are extremely well cut and you are asking me to split hairs here. Personally, this diamond would offer the best value for money.

    https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685701.htm

  18. John-
    July 15, 2016 at 2:39 pm

    Hi again Paul,

    Should I be worried about the diamond above (http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685701.htm) not being considered “eye clean”, with a small feather near the center-side, that is noticable to the keen eye? weighing between that and another http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685711.htm with near identical stats and less noticable inclusions, but a color grade of I instead of H.

    I’d go with the original one you linked; but i wasn’t sure if this is something i should be concerned with that i would ever even notice?

    Thank you very much for your help!

  19. Paul Gian-
    July 16, 2016 at 7:52 am

    I would say if you intend to look at it really closely all the time, the inclusion may be an issue. In normal viewing, the inclusions would be somewhat hard to detect. This would be a safer choice for mind cleanliness.

    https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685711.htm

  20. Paul Gian-
    August 4, 2016 at 2:09 pm

    Both designs will look identical. I think the James Allen melees are higher in quality though and that does matters.

  21. Paul Gian-
    August 5, 2016 at 12:49 am
  22. Paul Gian-
    August 5, 2016 at 7:36 am

    Yes. It has good cut precision and light return properties. Definitely 3.

  23. kay-
    August 5, 2016 at 2:23 pm

    Platinum or 14 carat white gold?

  24. Paul Gian-
    August 5, 2016 at 3:52 pm

    White gold for practicality reasons.

  25. Naz Locke-
    January 10, 2017 at 9:30 pm

    I had a question on smaller diamonds set on an eternity bands: should I worry about the 4C’s when looking for smaller diamonds? Does the type of gold matter in terms of brilliance? And, its seems that the examples below don’t have GIA certifcation. Are GIA certifications good for larger carat diamonds?

    For example: https://www.jamesallen.com/wedding-rings/womens-diamond/14k-white-gold-thin-french-cut-pave-set-diamond-eternity-wedding-ring-item-1481
    or

    https://www.jamesallen.com/wedding-rings/womens-eternity/14k-white-gold-ladies-028ctw-angled-common-prong-diamond-eternity-ring-item-56292

  26. Paul Gian-
    January 13, 2017 at 3:07 am

    With melees (small diamonds), it isn’t necessary to have a GIA grading report because it doesn’t make economic sense for them to be graded. i.e. the cost of grading is many times the cost of the diamond.

    With James Allen, you can be assured of the quality of the melees they use in the eternity bands. They are reliable and both designs you chose offer good value for money.

  27. Frédéric Siffert-
    April 14, 2017 at 8:34 am

    Hi Paul,

    I’ve followed your recommandations, and finally decided for this Diamond https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3809129.htm

    What do you think about it ?
    Thank you

    Frederic

  28. Paul Gian-
    April 14, 2017 at 9:37 am

    That’s a very well cut diamond and is eyeclean. Good choice!

  29. Frédéric Siffert-
    April 14, 2017 at 2:58 pm

    Thank you for your opinion, and I recommend to all people to carefully read your website before buying a diamond

  30. Kim-
    June 20, 2017 at 1:20 pm

    7223246706 –
    1166600222 – cost £1.3k more
    Hi Paul, thank you so much for the advice! I am now stuck.. Having looked at the some diamonds I am now choosing between the above 2. The above diamonds are eye clean. The first is much cleaner with no inclusions on the table .The second has a better cut and colour. Which should I choose? I keep looking online and the second has the super ideal cut. Will it really have so much better light return, fire and scintillation to make up for the costs and inclusions in the table? Help please!

    Kim

  31. Paul Gian-
    June 21, 2017 at 1:34 am

    You are making a huge mistake shopping like this: https://beyond4cs.com/buying-diamonds-blind/

  32. Kim Le-
    July 20, 2017 at 8:05 am

    Hi Paul, I took your advice, returned the stone and looked at the below 2 stones:
    AGS: 104092883042 G SI1 1.83
    AGS: 104084747041 F SI1 1.723

    Which would you choose?
    Stone one is not as clean as stone 2.

    Thanks,
    K

  33. Paul Gian-
    July 21, 2017 at 12:40 pm

    You need to provide me with tangible data like scope images if you want me to help you review the stone. Otherwise, I will just point you in the same article above. You probably want to email me as I tend to respond faster via emails.

  34. Denise-
    December 8, 2017 at 6:11 am

    Paul,

    I have recently started looking for a diamond ring. Thus far I have found your website to be extremely helpful to a novice such as myself. I have narrowed my selections down to four choices, and would like to know your thoughts on the best of the four.
    It’s a round cut 0.91 carat H VS2 Excellent the SKU numbers are as follows
    SKU 3601348
    SKU 3495043
    SKU 2859172
    SKU
    3460705
    I would also like to know your thought re James Allen vs White Flash.

    Would greatly appreciate your feedback.

    Denise

  35. Paul Gian-
    December 9, 2017 at 3:32 am

    None of these James Allen diamonds are well cut. They are all mediocre diamonds and will not offer the best sparkle.

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