Is the HCA Score Always Reliable For Diamond Selections?

For most online shoppers, you might have come across a diamond performance predictor called the HCA (Holloway Cut Advisor) tool to help you make your selections. This was a question which was posed to us about using the tool.

“Recently, I had some diamonds sent in for a physical review for light performance at James Allen.

score of 1.1 in hca

Here’s the 2nd diamond…

total visual performance of 2.6

When the gemologist gave me the report, I was surprised!

The better diamond was the 0.42 carat-I-SI1 diamond (1475263) due to its superb light performance with the great fire, brilliance and scintillation. It faces up completely eye clean and has a nice white color. The 0.41 carat-H-SI1 diamond (14753031) had just ok light performance. It faces up eye clean and has a nice white color, but it just doesn’t perform as good.”

I can’t understand how a HCA of 2.6 can be considered superb light performance with the great fire, brilliance and scintillation compared to the H of 1.1 & 1.4.

Isn’t it supposed to be simple geometry & physics of light reflection / refraction?


Answer: The HCA scores only act as a guideline and should be used as a rejection tool rather than a selection tool. Think of it this way. If the HCA score for a diamond is < 2.0, it results in a higher probability of finding a nice diamond. For HCA scores > 2.0, the chances of finding a great diamond are smaller. However, that’s not to say beautiful diamonds with a HCA score greater than 2 don’t exist.

Most people take the easier way and simply ignore scores higher than 2.0.

For example, if you choose to shop at Bluenile or any other online vendor where there are no pictures or sufficient data – most shoppers are shopping based only on the information found in a grading report. They would rather ‘play safe’ and ignore scores above 2.0 because they don’t have access to tools like idealscope or even better, an in-house review of the diamonds.

Personally, I believe that HCA by itself shouldn’t be used as an end all be all kind of tool but rather as a screening system to narrow down your diamond choices.

Let Me Show You Why the HCA Can Be An EPIC FAILURE

I want you check out the GIA report of a diamond with “great” looking proportions on paper. It’s a GIA triple excellent and there are no red flags based on the information presented in the GIA certificate.

ideal round diamond proportions poor light performance

Plugging in the proportions of the diamond into the HCA software…

screen shot hca software result

As you can see in the screenshot above, the HCA tool returns an excellent score of 1.9 for Total Visual Performance and describes the stone as “Excellent within TIC range”. And if you are wondering how the diamond would look like in real life, you are in for a shocker.

30X image round brilliant dark center

Click here to see complete details of the stone…

For your convenience, I had also extracted the corresponding ASET image. It critically reveals the light performance and cut deficits of the stone instantly.

dug out round diamond girdle aset

So much for scoring an “excellent” 1.9 on the HCA, this diamond is a total train wreck and I would classify it near the bottom of the barrel in the GIA triple excellent range.

Not only is the diamond displaying significant light leakage under the table, the girdle of the diamond had been severely dug out for weight retention purposes! This phenomenon is indicated by the huge amounts of green areas at the girdle and result in lesser brilliance.

The Holloway Cut Adviser often FAILS to eliminate diamonds that aren’t cut for optical performance. This should come as no surprise since the tool itself is meant to be used as a weeding tool instead of a selection tool.

Here are a couple more examples for you to check out for yourself. In all these cases, the HCA software returns a false positive. You can easily verify the diamond’s mediocre light performance with the ASET images.

I could go on and on to list hundreds of examples to show you the pitfalls of using the HCA software blindly. Hopefully, you get the idea now. When buying a diamond, it’s really foolish if you think the HCA tool is going to “magically” help you make the best selections possible without other tangible cut data.

Why The HCA Score For Diamond Selection Isn’t Everything

I will attempt to explain in plain English on some of the flaws in HCA:

1) HCA uses the average values of proportions/angles to generate its results. By doing this, the software is assuming a diamond that is perfectly symmetrical. In reality, diamonds have slight variations and deviations in the angles they are cut to.

If you have access to a Helium or Sarin Scan, you will see the deviations of the facet proportions. If you think about it, anything that is “human-made” will not be exactly the same. Furthermore, we are talking about cutting the hardest substance on Earth. There are bound to be degrees of inconsistencies in the diamond.

sample sarin scan

Sample Report of a Sarin Scan

When we are talking about diamonds, even a slight change in angles (<1 degree) can change the outlook of the stone and its performance.

2) Minor facets (lower girdle, upper girdle and star facets) are not taken into account during computation. For example, in real life, the length of lower girdle facets can impact how a diamond behaves under different lightings. A shorter lower girdle facet length would create broader flashes of light and a longer girdle facet length will create more pin flashes of light.

3) Inclusions and other properties. The software doesn’t take into account how inclusions can impact a diamond’s beauty. For example, it doesn’t tell you whether additional clouds are causing haziness issues in your stone or whether that crystal under the table facet is visible to the naked eye. Likewise, the HCA isn’t going to tell you if fluorescence has a negative impact on the stones appearance.

That said, diamonds themselves can have slightly different personalities even if they have ideal optics. For earrings, it would be best to match the diamonds to look similar. Since you had a professional gemologist review your choices at James Allen, they are your ‘eyes’ to help you select diamonds.

I think you need to give James Allen a call to discuss your concerns with them. They are the ones who had seen the diamonds physically and will be in the best position to provide you with further advice. Personally, I would trust what the gemologist says more than what the HCA scores tells me.

Paul

Buying diamonds blind is a bad idea. When shopping online, I highly recommend vendors like JamesAllen.com and WhiteFlash.com because they offer crucial information like videos and Idealscope/ASET images for you to make rational choices.

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51 Comments

  1. harry n.-
    September 16, 2012 at 2:21 am

    I tried inputting the data for a shortlisted stone from Kay-Jeweler here but couldn’t do so due to the lack of data. Can you help?

    It is a Leo Cut with 1.55 Carat Weight I Color and SI2 clarity.

    1.55 carat leo cut diamond from kays

    Below is the grading report that accompanies the diamond.

    leo diamond gemological science international grading report

    Harry

  2. Paul-
    September 16, 2012 at 4:01 pm

    The HCA tool is only applicable to 57 (58) facets round brilliant cuts. For the Leo diamond, it is a branded cut and cannot be used for assessment with the Hollway Cut Advisor.

  3. harry n.-
    September 17, 2012 at 4:13 am

    Thanks for the clarification!

    What do you think of the Leo cut and the choice that I had shortlisted?

  4. Paul-
    September 17, 2012 at 6:38 pm

    Have you seen the stone in person? When people go for branded cuts, it is usually a preference for how the diamond looks like in appearance.

    With that said, here’s my opinion on it:

    The magnified picture shows a stone with very poor optical symmetry. The Leo cut is a joke and is overpriced for the kind of quality it offers. Shopping at Kay Jewelers will guarantee that you will be overpaying significantly.

    In addition, the grading report for the diamond comes from an unknown source. Gemological Science International is totally unheard of to me. Why do you think the diamond was not sent to renowned labs GIA or AGS for grading? Is there something that they are hiding?

    Chances are, the stone is graded loosely much like the case of IGI or EGL stones. When jewelers choose to use grading labs like these, I will usually avoid them since you won’t know exactly what you would be getting. They graded this particular stone as a SI2, it looks more like an I1-I2 by GIA’s standards at best.

    http://beyond4cs.com/grading/difference-between-gia-ags-egl-igi/

    Most of the time, these reports helps the jewelers sell rings for more at the expense of un-educated consumers.

    http://beyond4cs.com/loose-diamonds/grade-bumping-scams/

  5. Pam-
    June 3, 2015 at 7:38 pm

    What do you think of pricescope.com members swearing by HCA and pushing this tool as a decision maker? I have seen plenty of people be discouraged from buying certain stones based solely on these numbers before being seeing in person. After working for a jeweler I have seen pricescope advised newbies coming in to see diamonds and basing their choices on the HCA number vs. the actually brilliance and quality of the stone.

  6. Paul Gian-
    June 4, 2015 at 2:56 am

    With all due respect, most people on such community boards don’t exactly know what they are doing or have a proper understanding about diamonds. Sometimes, some advice that are dished out actually does more harm than good but I digress.

    Anyway, the HCA tool is pretty basic and it jives well with people who are clueless about buying diamonds. This is because it gives them some tangible data about a diamond’s performance even though it only makes use of limited data inputs to do so.

    I personally don’t think it is an end all be all kind of tool. The thing about lay people trusting their own eyes when viewing a diamond physically is that lighting conditions can sometimes be manipulated and misleading in itself. i.e. poorly cut diamonds can actually be made to look nicer under certain types of lighting.

    Where possible, I do recommend obtaining as much data about a diamond as possible. This includes viewing diamonds in various kinds of lighting condition for prolong periods of time, ASET, Idealscope, HCA score and etc… Granted, it may not always be possible because of physical constraints especially when it comes to buying diamonds online.

  7. Yoshi-
    January 6, 2016 at 1:53 am

    Hi Paul,

    Is there ever an occurrence where the opposite is true? For instance, I have been looking at several GIA triple excellent reports, for an upcoming purchase. Using the HCA score as a guide, I have never seen anything lower than a 2.3. Is it possible to have a case where the HCA yields a higher score (i.e. 5 or 6) on a triple excellent cut, but the diamond has high brilliance potential in reality? Thanks for the guidance, and great site!

    Yosh

  8. Paul Gian-
    January 6, 2016 at 5:50 am

    I haven’t seen any diamonds with high HCA scores that have great light performance. In a way, the Holloway Cut Advisor weeds out the lousy stones but it doesn’t help you pick out the great stones. You’ll need an ASET or Idealscope for this purpose.

  9. Paul Gian-
    May 5, 2016 at 2:23 pm

    Both are mediocre stones.

  10. Chris-
    May 5, 2016 at 3:10 pm

    Hi Paul,

    Thanks for getting back so quickly. I am surprised at your opinion. Will you please elaborate as to why your consider both of these mediocre?

    I am in the process of deciding between these two and thought specwise they are excellent.

  11. Paul Gian-
    May 6, 2016 at 1:45 am

    Experience. Once you viewed enough diamonds and correlate them to real life light performances, you will be able to do it too.

    Proportions wise, both have already failed my 1st stage of filtering. The videos simply confirmed it.

  12. Paul Gian-
    May 6, 2016 at 1:04 pm
  13. Chris-
    May 6, 2016 at 2:38 pm

    Ok, hole you didn’t take offense to my previous comment…not judging your opinion at all. I have found your recommendations for proportions and am having James Allen search for a stone that meets the specs. For 1026284, will you please tell me which specifications in your opinion make it fail in your first stage?

    Thanks!

  14. Paul Gian-
    May 8, 2016 at 3:03 pm

    None taken. I’m trying to be objective in my comments.

    Read these: http://beyond4cs.com/shapes/round/ideal-proportions/
    http://beyond4cs.com/step-by-step-guide/

  15. Paul Gian-
    May 14, 2016 at 12:00 am

    The James Allen stone isn’t well cut. As for the Bluenile stone, shopping blind is just a bad idea.

    http://beyond4cs.com/reviews/blue-nile/

  16. Shawn-
    June 2, 2016 at 8:23 pm

    Hi Paul,
    Thank you for all this information. I’m debating between two stones from James Allen.

    https://www.jamesallen.com/loose-diamonds/round-cut/0.72-carat-k-color-vs1-clarity-excellent-cut-sku-1020458

    https://www.jamesallen.com/loose-diamonds/round-cut/0.72-carat-k-color-vs1-clarity-excellent-cut-sku-1020458

    Please let me know what you think about these and which one you’d pick. I plan to set it in 14k yellow gold with white prongs.

    Thank you for all the help!

  17. Paul Gian-
    June 3, 2016 at 1:51 am

    Both urls point to the same stone. It’s a decent diamond.

  18. Shawn-
    June 4, 2016 at 2:15 am

    Paul,
    Could you please tell me which is a better stone in terms of sparkle and colour (appear most white)? it will be in yellow gold setting, I would go with the K diamond, but a little afraid of it looking yellow. Some people are saying it might appear yellow. What do you think? What do you think is the best deal for the price and performance? Sorry for so many questions, but as an expert I think you know better than anyone I know. I really appreciate the help. Thank you!!

    https://www.jamesallen.com/loose-diamonds/round-cut/0.72-carat-k-color-vs1-clarity-excellent-cut-sku-1020458

    https://www.jamesallen.com/loose-diamonds/round-cut/0.73-carat-j-color-vs2-clarity-excellent-cut-sku-1137180

    http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3634229.htm

  19. Paul Gian-
    June 4, 2016 at 5:25 am
  20. Matthew Hrehor-
    June 26, 2016 at 1:28 am

    Hi paul,
    I am really having difficulty comparing diamonds in store to online. Could you please give me some advice on the better of these diamonds?

    Instore diamond
    http://www.gia.edu/cs/Satellite?pagename=GST%2FDispatcher&childpagename=GIA%2FPage%2FReportCheck&c=Page&cid=1355954554547&reportno=3225002577

    Online diamond
    http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685704.htm

    I realize how much better the whiteflash one grades on the HCA, but my girlfriend saw the GIA stone and loves it. Shold I be worrying about appeasing her or will the whiteflash stone make a significant difference in a rose gold halo? Both are in the same price range.
    Thank you!

  21. Paul Gian-
    June 26, 2016 at 7:28 am

    One is a poorly cut diamond while the other White Flash option is fantastic.

  22. Matthew J Hrehor-
    June 26, 2016 at 9:46 pm
  23. Paul Gian-
    June 27, 2016 at 12:59 pm

    This would be the only diamond that passes my cut standards to be purchase worthy.

    http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3685704.htm

    The other White Flash diamond isn’t well cut enough and there’s no supporting cut information for the other unknown stone.

  24. James-
    July 14, 2016 at 7:35 pm

    Hi Paul,

    Would you recommend this stone just based off GIA report.

    http://www.gia.edu/cs/Satellite?pagename=GST%2FDispatcher&childpagename=GIA%2FPage%2FReportCheck&c=Page&cid=1355954554547&reportno=2141066141

    Also, should grading date be something I should be concerned about?

    Thanks

  25. Paul Gian-
    July 15, 2016 at 3:07 am

    No. Proportions aren’t ideal.

    Secondly, yes. The dated report may be a concern. I want to know why it is dated so long ago if I were shopping for a diamond myself.

  26. Paul Gian-
    July 20, 2016 at 5:11 am

    The first diamond is the better option in terms of cut quality. The feather may not be eyeclean though.

  27. Lewis-
    July 21, 2016 at 7:51 pm

    Thank you Paul for your quick and honest response,
    I don’t even want to question if the diamond will be eye clean or not so i have decided to disregard sl2 and try to look for an eye clean sl1,

    i have found 2 more that are very similar in specs but again not sure which one will perform better.

    https://www.jamesallen.com/loose-diamonds/round-cut/0.91-carat-h-color-si1-clarity-excellent-cut-sku-1896831

    https://www.jamesallen.com/loose-diamonds/round-cut/0.91-carat-h-color-si1-clarity-excellent-cut-sku-630268

    personally i think the 1st one but i really don’t know,

    Cheers,

  28. Paul Gian-
    July 22, 2016 at 1:43 am

    Neither. You are running around in circles. I did a search for you and would recommend this stone: https://www.jamesallen.com/loose-diamonds/round-cut/0.90-carat-g-color-vs2-clarity-excellent-cut-sku-1844151

  29. August 25, 2016 at 5:26 am

    Hi Paul,
    Relying on Enchanted info is a bad move. e.g the 1.5ct G SI1 – no way does the stone photographed match the 61% table on the GIA cert. I am happy to have HCA criticized, but please use some stones in your hand rather than mixed up sources like the ones you have used.
    Kind regards
    Garry Holloway

  30. Paul Gian-
    August 25, 2016 at 1:24 pm

    Hey Gary,

    Thanks for dropping by and leaving your comment. I’ve checked the url listing again. Gosh, I did make a mistake there and slipped up by assuming the images were correct without doing a proper verification against the proportions. I’ve updated the post.

    Paul

  31. Jamie-
    October 8, 2016 at 9:37 am

    Hi Paul. Thanks for sharing your expertise! Do you consider the pavilion angle of 41.4 in the following stone a deal breaker? Thanks so much for your input.

    Round brilliant graded by GIA as follows:
    .80
    Cut Ex
    Symmetry Ex
    Polish Ex
    Depth perc. 61.8
    Table percentage 56
    Crown Angle 34.5
    Pavilion Angle 41.4
    No fluorescence
    Thin to medium girdle

    Thanks so much. I appreciate your input!

  32. Paul Gian-
    October 8, 2016 at 2:55 pm

    Yes. It definitely is. There’s no way I would even consider buying a diamond with these proportions.

  33. Jaime-
    October 8, 2016 at 7:15 pm

    Thanks so much for your input! I needed confirmation that I should steer clear of it. I am curious… If the pavilion angle was less steep (say 40.9 or so) would this be a decent stone? (all other proportions equal) Thanks!

  34. Paul Gian-
    October 9, 2016 at 2:01 am
  35. Christian-
    October 21, 2016 at 9:20 pm

    Hi Paul – very informative website!

    Here is an example of a diamond that gets 4 Excellents on the HCA (is this quite rare?).

    https://www.jamesallen.com/mobile/loose-diamonds/round-cut/1.00-carat-i-color-vs2-clarity-excellent-cut-sku-1953420

    Is it worth following up with an ASET image, or do you think the symmetry will mean it’s not a great performer?

    Any comments welcome!

    Thanks
    Christian

  36. Paul Gian-
    October 24, 2016 at 12:24 am

    I can tell you that this diamond is going to be bright and will have good light performance. The symmetry will not impact the light performance much in this particular case. However, the proportions of this diamond 59/59 will result in a different sparkle/scintillation pattern compared to a typical ideal cut diamond that I would buy. The 59% depth is the reason why the HCA rating rewarded it for spread but it isn’t a good enough reason for me to buy it.

  37. Caleb-
    October 25, 2016 at 6:55 am

    Hi Paul. Great site! I have the following diamond I’m interested in getting and would like your advice if it’s a wise buy. Should I be worried that the crown angle is beyond your recommended 35? Thanks.

    Color: F
    Clarity: VS1

    Depth: 62.4
    Table: 56
    Crown angle: 36.5
    Pavilion angle: 40.6
    Girdle: Medium faceted, 3.5%

  38. Paul Gian-
    October 25, 2016 at 7:26 am

    Yes. The crown angles are way too high.

  39. Tony-
    November 30, 2016 at 5:34 pm

    Hi Paul,

    I’m looking to purchase a diamond from bluenile.com

    I need your advice on it as soon as possible, and also if you have any information about the credibility of the site as well. I’m not confident in purchasing a diamond online and would appreciate your help.

    Down below is the link of the diamond I have in mind
    http://www.bluenile.com/diamond-details/LD06703289

    Thank you

  40. Paul Gian-
    December 1, 2016 at 2:50 am

    It’s a decent stone but not well cut enough by my standards. I did a search for you and would recommend these diamonds instead:

    http://beyond4cs.com/go/bn-LD06199853/
    http://beyond4cs.com/go/bn-LD06832897/

  41. bill-
    December 5, 2016 at 5:42 pm

    GIA 2247184620 $2900
    GIA 1245017666 $2670
    GIA 7238160368 $2600

    Bluenile diamonds. I am deciding to buy all 3 and have them evaluated for light performance. What would you suggest for how this is done as I could not find a site that links me a “local” specialist. lastly, w/o having seen them or imaging, are there any concerns regarding their inclusions?

    Bill

  42. Paul Gian-
    December 6, 2016 at 6:14 am

    I hate it when people abuse a vendor’s return policy this way. It creates unnecessary costs for them, hassle for yourself and costs for yourself too. It’s not that hard; just that with their signature line and you saved all your trouble.

    http://beyond4cs.com/reviews/blue-nile/signature-diamond/

  43. Paul Gian-
    January 21, 2017 at 7:57 am

    The 4th diamond option is the best among the shortlisted choices. That’s the one I would go for.

  44. Kris-
    January 21, 2017 at 3:34 pm

    Thank you Paul!!

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