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Jun
22

Diamond Cut Quality

Posted by: | Comments (290)

If you’re searching for the perfect diamond, then please contact me, and let me know your budget and what you’re looking for. I’ll sift through hundreds of thousands of diamonds online from vendors like James Allen and Blue Nile, and find the perfect stone for you and your budget. Unlike the other sites, I’m not looking to sell you anything – my advice is objective and in your best interest.  You have nothing to lose and a larger diamond or saving hundreds of dollars to gain.

Bottom Line Recommendation:

  • Diamond Cut Grade: For GIA Certified Diamonds, a cut grade of “Very Good” will look great.  You will, however, be able to notice an improvement in brilliance by upgrading to “Excellent.”  For AGS Certified Diamonds, a cut grade of “Excellent” will suffice, but you will notice added brilliance by upgrading to “Ideal”
  • “Triple Excellent” or “Triple Zero” look pretty on paper, but you shouldn’t pay extra for Excellent (or AGS Ideal) Polish or Symmetry.  You cannot detect the difference between Good (AGS Very Good) Polish and Symmetry and Excellent (AGS Ideal) Polish and Symmetry with your naked eye.  In most cases you need a microscope to detect the difference.
  • For Round Brilliant Cut Diamonds, don’t give too much credence to an online vendor’s cut grade.   Only focus on the GIA or AGS cut grade on the certificate.

Diamond Cut – a Definition

Diamond Cut refers to how well proportioned the diamond is.  For example, what percentage of a diamonds diameter is its depth?  What are its various angles and how do they interact with one another?  While these may seem like esoteric questions, these are the essential factors that determine how beautiful your diamond will be.  For a great visual representation of why these issues matter, have a look at James Allen’s page on Diamond Cut.

Diamond Cut Grade — All that Matters

Until January 1st, 2006, you basically had two options when it came to diamond cut grade.  You could either buy a diamond with an AGS certificate and trust their diamond cut grading system, or you could learn about the various proportions of diamond cut and trust your own eduction about what numbers translated into a beautiful diamond.  On that day, though, the GIA introduced a new certificate format that included their very own diamond cut grade.  They claim that their Diamond Cut Grade system is based on 15 years of research testing and retesting different combinations of measurements with real life light performance tests.  ags_ogi_reportAs opposed to the old AGS system which simply defined what an “ideal” diamond is and then gives lower grades the farther away from that “ideal” the parameters are (see table to the left), the GIA system does not have any one single definition of perfection.  They claim that in their research various differing combinations of proportions equally produced diamonds that reflected the most light.  So while in the old AGS model, a diamond with a table size of 60% is automatically penalized to a Diamond Cut Grade of “2,” (on a scale from 0 to 9), with the GIA model, there’s still a chance the diamond could receive an “Excellent” grade if the rest of the parameters are the best possible parameters that combine with a 60% table.

To be fair, in the middle of 2005, AGS also realized that their way of doing things was antiquated.  So beginning on June 1st, the AGS lab began offering its certificates with a new light performance-based cut grade.  As it would turn out, though, this new method made it even more difficult for stones to receive the coveted “Ideal” grade for cut.  Thus, when the GIA cut grade was released a half a year later with its more elegant solution, AGS lost much market share to the GIA.

Realizing their error and almost facing extinction, the AGS lab in 2008 decided to copy the GIA and began offering a “new” proportions based cut grade.  I write “new” in quotation marks because, really, there was nothing new about it.  The AGS cut grade prior to 2005 had always been proportions based.  They simply re-introduced it, just this time with more flexibility. They made the smart decision to mimic the GIA and award Ideal cut grades to different non-concentric combinations of proportions.

In my opinion, the GIA & AGS systems are clearly a much more elegant solution to the question of what cut proportions produce the most beautiful diamonds.  And the fact is, it’s a more elegant solution than your typical diamond dealer’s instincts, as well.  What I mean is, before GIA introduced their cut grade, most diamond dealers thought about cut grade the same way the AGS did.  They had in their mind what was the perfect set of parameters, and basically, diamonds got uglier the further they strayed from that ideal.  This revelation of how GIA Diamond Cut Grade worked was a boon to diamond manufacturers as well.  Now, the cutters had more options when assessing a piece of rough for cutting.  If a diamond with a 57% sized table couldn’t fit into a certain piece of rough and still maintain the weight category, then they could try a diamond with a 60% table and see if that would maintain the weight.

For those of you looking to buy a diamond without a certificate, here’s a very dumbed-down, but reliable rule of thumb.  Just remember “60/60.”  That means 60% table and 60% total depth.  While this falls out of the “0″ and “1″ cut grade of the old AGS standard, it is the basic rule of thumb that diamond dealers always use.  You can allow for about 2% plus or minus from the 60%, and make sure the girdle size is either thin or medium, but not thick.  With these simple rules, you can be assured you will end up with a very beautiful diamond.

If you have any questions, please post them in the comments below.  I will usually respond within 24 hours.

Related posts:

  1. Taking The Diamond Quality Challenge on the Street in Times Square NYC!
  2. Q&A: How to Get the Same Quality as Hearts on Fire (HOF) for a Fraction of the Cost
  3. Dude, if You’re Gonna Steal, at Least go for Quality
  4. AGS
  5. Diamond Symmetry

Comments

  1. Joe says:
    January 9, 2012 at 3:49 am

    Hi Ira,
    Question, when considering a Heart shaped diamond does the 60/60 rule still hold true? These two are within my budget, the second has better color but does not meet the rule:

    http://www.jamesallen.com/diamonds/F-VS1-Ideal-Cut-Heart-Diamond-1381787.asp
    http://www.jamesallen.com/diamonds/E-VS2-Premium-Cut-Heart-Diamond-1440655.asp

    Also, Table & Depth are always listed as a percentage but I’ve never figured out why – can you explain this to me (or link it to somewhere on your site if I’ve missed it)?

    Thanks again,
    -joe

    Reply
    • Ira Weissman says:
      January 9, 2012 at 12:15 pm

      Hi Joe. No, everything gets thrown out of the window for hearts. Just buy one that looks good to you. Depth is the depth of the stone (distance from the table to the culet) divided by the width. The width on a round is just the diameter. In a rectangular diamond, the shorter side is used. I’m actually not sure which dimension is used on a heart shape. Table is the size of the table facet as a fraction of the total width of the stone (same story here regarding “width” as with the depth %).

      Reply
  2. HeatherB says:
    January 7, 2012 at 9:45 pm

    Hi Ira,
    I’ve been lurking on your site for a while now and appreciate all of the great info. My boyfriend and I are looking at a preowned (but barely worn) ring with an EGL USA certified diamond (I know you don’t care for EGL so much, but it comes in the setting I love and much cheaper than retail). The ring priced at $9.5k seems like a good value considering the overall quality of the stone and the fact that it comes with a Tacori setting which would retail for $4k without a center diamond, but I want to know if the low crown angle is a concern – here are the specs per the EGL cert:
    Weight 1.73 CT
    Shape ROUND BRILLIANT
    Color H
    Clarity SI2
    Measurements 7.85 x 7.8 x 4.71 mm
    Depth 60.2%
    Table 59%
    Crown 10.9%
    Pavilion 44.8%
    Crown Angle 27.2°
    Pavilion Angle 42°
    Girdle MEDIUM TO SL. THICK FACETED
    Polish GOOD
    Symmetry GOOD
    Fluorescence N/A
    Culet N/A
    Cut Grade N/A

    What do you think? Does it sound like a good buy?

    Thanks!
    Heather

    Reply
    • Ira Weissman says:
      January 8, 2012 at 10:24 pm

      It’s not a good buy, because it’s almost for sure the GIA equivalent of a J I1. Here’s an I I1 on James Allen that’s $7210:
      http://www.jamesallen.com/diamonds/I-I1-Good-Cut-Round-Diamond-1407830.asp

      Reply
      • HeatherB says:
        January 10, 2012 at 5:35 am

        Ira,
        Thanks very much for your reply. Is that an inclusion I see toward the left/center area of the stone on James Allen?

        If the seller of the ring I was looking at with the EGL stone is willing to take $8000-8500 for it, and considering the ring also comes with the setting we really want, which we’d have to pay $4000 for if purchased separately from a Tacori dealer, then that might be worth considering right? We are also going to confirm that there are no visible inclusions before proceeding. Also, not sure if this holds any weight since it was put out by UGS, but the retail replacement value of this stone is listed at $16,290.

        Reply
  3. Simba says:
    January 6, 2012 at 7:51 pm

    Hi Ira

    What do you think of the following diamonds?

    http://www.jamesallen.com/diamonds/J-SI1-Ideal-Cut-Round-Diamond-1430300.asp

    http://www.jamesallen.com/diamonds/J-SI1-Premium-Cut-Round-Diamond-1425863.asp

    http://www.jamesallen.com/diamonds/J-SI1-Ideal-Cut-Round-Diamond-1430300.asp

    I am looking at the following setting:
    http://www.jamesallen.com/engagement-rings/pave/18k-White-Gold-0-66ct-Rounded-Engagement-Ring.html

    thanks for your help!

    Reply
  4. Douglas says:
    January 6, 2012 at 6:33 pm

    Hi Ira,

    I am looking for a Princess Cut diamond that looks best to the naked eye. I am looking for something in the 1 carat range with a budget of $4k for the diamond itself.
    Color: I or better
    Clarity: SL1 or better

    Which of these diamonds do you think is best?
    http://www.jamesallen.com/diamonds/H-VS1-Good-Cut-Princess-Diamond-1421073.asp
    http://www.jamesallen.com/diamonds/I-IF-Good-Cut-Princess-Diamond-1450597.asp
    http://www.jamesallen.com/diamonds/I-VVS2-Good-Cut-Princess-Diamond-1440411.asp

    Reply
  5. bindu vij says:
    January 5, 2012 at 7:45 am

    Hello Ira,

    Looking for a round cut diamond with these specs:
    G colour or better
    VS2 or better clarity
    Excellent or ideal cut
    1 to 1.15 carat
    $7.5k budget 0r under
    A beautiful looking diamond to the eye is the most important factor here.

    Your help will be greatly appreciated

    Reply
    • bindu vij says:
      January 5, 2012 at 9:19 am

      http://www.jamesallen.com/diamonds/I-VS2-Premium-Cut-Round-Diamond-1447240.asp

      I found this diamond.. can you please comment on what you think.
      Thanks

      Reply
    • Ira Weissman says:
      January 5, 2012 at 11:12 pm

      Are you open to an eye clean SI?

      Reply
      • bindu vij says:
        January 6, 2012 at 5:57 am

        yes please send me the link .thank u

        Reply
        • bindu vij says:
          January 6, 2012 at 8:07 am

          Hi Ira,
          i was also looking for princess cut diamond and found out i get more quality for the same price. why is princess cheaper than round . what do u think which one is better princess or round. i also read that princess cut does not sparkle as much as round cut diamond . i would appreicate if u can solve my confusion . Can u look at this princess cut diamond and suggest me
          http://www.jamesallen.com/diamonds/F-VVS1-Premium-Cut-Princess-Diamond-1437445.asp

          Reply
          • Ira Weissman says:
            January 6, 2012 at 11:33 am

            Princess costs less than round because the yield from rough is much higher. See my article “Truth about Diamond Shapes”.

            Plus, for the same money, you could probably get a HEAVIER princess cut than a round, but it won’t necessarily give you more SURFACE AREA. Princess cuts are typically 70-75% deep (depth divided by the shorter side) whereas rounds are typically between 59-63% deep (depth divided by diameter). So rounds give you more diamond showing per carat.

            And yes, rounds are more brilliant.

            Here’s what I like:
            http://www.jamesallen.com/diamonds/I-SI1-Ideal-Cut-Round-Diamond-1444963.asp
            http://www.jamesallen.com/diamonds/I-SI1-Premium-Cut-Round-Diamond-1446938.asp

          • bindu vij says:
            January 7, 2012 at 1:43 am

            Hi ira ,
            thank u so much for the recommendation . i did like the 1.21 carat diamond for the price it is . when i do see the GIA REPORT the inclusion are significant . are they like completely eye clean should i be concerned because its says additional inclusion are not shown graning is not shown . can u help me with that.

          • Ira Weissman says:
            January 8, 2012 at 10:18 pm

            GIA inclusion plots are useless for determining whether or not a stone will be eye clean. They only tell you placement and type of an inclusion where the most important factors are color and relative strength/opaqueness. In fact, a very busy inclusion plot is usually a GOOD thing because it means the SI2 is very spread out and weak and therefore not visible with the naked eye. If an SI2 was concentrated in one small area, it would mean that it’s very strong and probably eye visible.

          • bindu vij says:
            January 7, 2012 at 6:19 am

            Sorry to bother you.. I had few more questions:

            1) comparing the 2 round diamonds : one I has send you earlier with one you recommended

            http://www.jamesallen.com/diamonds/I-VS2-Premium-Cut-Round-Diamond-1447240.asp

            http://www.jamesallen.com/diamonds/I-SI1-Ideal-Cut-Round-Diamond-1444963.asp

            Difference of 500 $ in price for 0.09 more carat weight ( 1.21 vs 1.12) and compromising clarity ( SI1 vs VS2).

            Which one do you think is a better deal and why?

            2) I would like a 18K white gold ring suggestion if possible for the solitare ( is knife edge better or comfort fit).

            3) Do the Inclusions you see on GIA report matter?

            4) Some diamonds have a bluish or brown hue when you look with a naked eye on james allen ( but no flouresence). Its also in one of the above diamonds. Is that of concern?

            5) I have never bought any ring online.. but was impressed with JA website and reviews. How does it compare to retail stores when you consider- returns, repairs, warranty, cleaning, upgrades, reliability etc..

            Thanks a lot for your prompt replies. You have been very helpful in the decision process.

          • Ira Weissman says:
            January 8, 2012 at 10:22 pm

            1) http://www.jamesallen.com/diamonds/I-VS2-Premium-Cut-Round-Diamond-1447240.asp is a better deal because the difference in diameter is not noticeable and it’s cheaper
            2) It’s completely subjective. Whatever looks nicest to you.
            3) No. See my other response to your other comment.
            4) No, it’s just an issue of photography. You won’t see that.
            5) They’re super easy to deal with. I’ve bought some things from them and returned them pretending to be a customer to check out their service. It was impeccable.

          • bindu vij says:
            January 8, 2012 at 11:54 pm

            Thanks for your reply.

            1) How do you determine if the diamond is eye clean on JA website – is it using virtual loupe ( many times you see a few dark spots near circumference- r they relevant). is the above I VS2 diamond eye clean in your opinion?

            2) regarding dimensions for round diamonds- is there a range for depth, table and girdle thickness to be looking for? I notice the I SI1 1.2 crt diamond you had suggested has table 57%, whereas IVS2 1.12 crt has table 60%.

            I am almost there. Do you suggest to talk to customer service before buying it.

            Bindu

          • Ira Weissman says:
            January 9, 2012 at 11:44 am

            1) From the experience of seeing hundreds of thousands of diamonds over my career both with and without a loupe. Above VS2 will always be eye clean.
            2) Don’t worry about that. Just stick to Excellent cut from GIA or Ideal from AGS.

  6. Russ says:
    January 3, 2012 at 4:31 pm

    What do you think of this diamond?
    http://www.jamesallen.com/diamonds/I-VS2-Ideal-Cut-Round-Diamond-1434884.asp

    Is the strong fluoresence going to be a good thing or a bad thing?

    Would any of these be a better buy?

    http://www.jamesallen.com/diamonds/I-SI1-Ideal-Cut-Round-Diamond-1447291.asp
    http://www.jamesallen.com/diamonds/I-VS2-Ideal-Cut-Round-Diamond-1438984.asp
    http://www.jamesallen.com/diamonds/I-VS2-Ideal-Cut-Round-Diamond-1430841.asp

    Thanks

    Reply
  7. Dean says:
    December 30, 2011 at 7:59 pm

    I’m looking for cushion cut diamond that is visually a square. It doesn’t have to be exactly a square, just need to look like it.

    color: g,h
    clarity: vs1, si2
    carat: about 1

    price: under $4000

    what do you think is best out there? here are a few that I’m looking at.

    1. http://www.bluenile.com/diamond-search?pt=setform#diamonds_pid=LD02190237

    2. http://www.bluenile.com/diamond-search?pt=setform#diamonds_pid=LD02073998

    3. http://www.jamesallen.com/diamonds/H-SI1-Ideal-Cut-Cushion-Diamond-1397280.asp

    4. http://www.jamesallen.com/diamonds/H-SI1-Ideal-Cut-Cushion-Diamond-1397403.asp

    5. http://www.jamesallen.com/diamonds/G-SI1-Ideal-Cut-Cushion-Diamond-1380006.asp

    Reply
  8. Jamie says:
    December 30, 2011 at 9:04 am

    Hello Ira,

    Looking for a princess cut with these specs:
    G colour or better
    VS2 or better clarity
    Excellent or ideal cut
    1 carat
    $5k budget
    A beautiful looking diamond to the eye is the most important factor here.

    Your help will be greatly appreciated

    Reply
  9. Kevin says:
    December 30, 2011 at 1:47 am

    Please advice between these stones (price range is $1000 – $1700) and really want to stay above .5 carat if possible. Or if you have additional recommendations, I would appreciate it. Thanks

    1362914
    1436343
    1437939
    1443093
    1444038
    1447165

    Reply
  10. Raymond says:
    December 28, 2011 at 1:05 am

    Hi Ira,

    I am looking for a cushion cut diamond 1.4 – 2.0 carats. I am willing to spend up to $30,000 for something very nice. I was thinking excellent cut, F color, VVS2/VS1. Is it better to be G/H and VS1/VS2? At what point will the inclusions be visible on a larger cushion cut?

    Thanks for your help.

    Raymond

    Reply
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