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Does low HCA score means a good diamomd?

Discussion in 'RockyTalky' started by Diamondfresh, May 16, 2019 at 4:23 AM.

  1. Diamondfresh
    Rough_Rock

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    by Diamondfresh » May 16, 2019 at 4:23 AM
    20190516_160641.jpg I am interested in this diamond but the HCA score is around 5. Price is approx USD 8,500. Does high HCA score means the diamond is not as good?
    Screenshot_20190516-162429_Gallery.jpg
     
    


    


  2. kmoro
    Brilliant_Rock

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    by kmoro » May 16, 2019 at 4:46 AM
    Diamonds are cut so that the facets act like mirrors ... there are certain angles that these mirrors need to be in order to reflect light in an optimal way. The HCA gives an indication of how well the angles of your diamond can be expected to work together. With GIA, there is rounding of numbers, so the HCA can not always be accurate ... it is a rejection tool only ... it can not be used to choose a diamond but is quite effective in weeding out definite poor performers. If you have a diamond that scores 5, it should be rejected as you can find much better.

    Here is a super-ideal A Cut Above 1.071 ct G eye-clean VS2 around the same price .... it is gorgeous with a very small table that is highly sought after by those who love diamond fire ... you would be with a top-notch vendor and a $1 upgrade policy ... imo, this would be a much better option. This is AGS graded, meaning it has been evaluated for light performance, no rounded numbers, no guess work or HCA required, and has the top score.

    https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3999639.htm
     
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  3. Diamondfresh
    Rough_Rock

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  4. sledge
    Ideal_Rock

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    by sledge » May 16, 2019 at 7:37 AM
    Although the overall depth for this stone is within acceptable criteria, the bigger issue is it's "pavilion heavy".

    The pavilion is 41.6, resulting in 44.5% pavilion thickness. At 41.2+ angle things go really wonky. So even if the other properties are great this isn't a good performer.

    Even if you were chasing a 60/60 stone with 33/41 combo, you'd want to make sure the actual values didn't cross that 41.2 threshold.

    While HCA doesn't always guarantee a winner, in this case its score is indicating an issue and you'd be wise to listen.

    I would pass on the stone in question.
     
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  5. lovedogs
    Ideal_Rock

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    by lovedogs » May 16, 2019 at 10:33 AM
    I definitely would pass on that stone.
     
  6. diamondseeker2006
    Super_Ideal_Rock

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    by diamondseeker2006 » May 16, 2019 at 3:06 PM
    Look for GIA Ex cut stones within these parameters:

    Table 54-57
    Depth 62-62.3
    Crown angle 34-35.0
    Pavilion angle 40.6-40.9
     
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  7. TimMD
    Shiny_Rock

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    by TimMD » May 16, 2019 at 3:43 PM
    I agree with the others, I think there are better stones to be found.

    @diamondseeker2006 Do not want to thread jack but since coming back around a few months ago, I have been meaning to say hello, glad to see a familiar face after all these years and I always appreciated your sound advice and friendly comments =)2
     
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  8. OoohShiny
    Ideal_Rock

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    by OoohShiny » May 17, 2019 at 3:16 AM
    That seems a more restrictive set of parameters than I've been using/recommending - I've been suggesting these!

    T 54-58%
    D 60-62.4%
    P 40.6-40.9 degrees
    C 34-35 degrees (up to 35.5 with 40.6 crown angle)
     
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