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HCA question?

Discussion in 'RockyTalky' started by HornAround, Apr 23, 2009.

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  1. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    I know its used for rejection, not selection. I''m curious about one thing though. When you enter the dimensions of different diamonds you will get the usual assortment of colors, however, sometimes the color red is absent. Does that mean there isn''t as much fire? Does the red being excluded mean it''s not worthy of it?
     
    


    


  2. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    I would go more by the overall proportions and images if you have them rather than the HCA, it cannot physically see the diamond and can''t say with any certainty that a particular diamond will behave in a certain way. You can get a fair idea from the proportions but thats all.
     
  3. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    I just wonder if I'm splitting hairs on some of these diamonds.
     
  4. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    for instance,


    diamond A has the dimensions of

    Depth-62.8
    Table-56
    Crown-35
    Pavilion-41.2

    If you plug those into the HCa you get a 1.5. it falls directly under in the AGS 0 line, yet there is no red.

    Diamond B has the dimensions consisting of

    Depth-61.2
    Table-56
    Crown-34
    Pavilion- 40.8

    When those numbers are plugged you get an HCA score falling just outside the AGS line, yet it has more red under it.

    Judging from the numbers alone, which diamond would you say is better?

    I'm only trying to see why one certain diamond is worth more than the other providing the 3 C's are the same.
     
    


    


  5. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    The first diamond is what we call a steep deep, the angles won't normally work that well together, light leakage is often the result. Actually my results with the HCA are 3.6 not 1.5, these proportions won't score under 2 usually and also the diamond has too much depth. Try it again entering the figures above and see what you get.

    So definitely to me the second diamond is the best one.

    The redder coloured area you describe is explained here if you haven't already come across this explanation.

    http://diamonds.pricescope.com/ideal.asp
     
  6. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    Do you maybe have a typo in these numbers? I put the numbers of the first stone into HCA and came up with a 3.6. It still falls in the GIA Excellent box, but not the AGS0. GIA has wider parameters to still recieve an excellent on cut, and some of these combinations don't always work as good as others. The first stone you list is a little deep to be an AGS0.

    All the HCA can do is try and predict how a diamond will perform, you still need visual data to see that it will, in fact, perform well. That is why pictures, IdealScope and ASET images are so helpful.

    So from the numbers, if they are correct, all we can really say is that the second stone has a higher probability of performing better.
     
  7. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    I think there must be Jet, proportions like that aren''t going to score below 2 anyway.
     
  8. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    That's what I thought and why I tried the numbers in HCA--I couldn't believe a depth of 62.8 would score under 2. I'm still learning about diamonds, but I know that a certain knowledgable PS'er usually recommends staying under 62.4. I wonder who that would be? [​IMG]
     
  9. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    Ooops, I put the specs for the wrong diamond. Here are the ones for diamond A

    Depth-61.2
    Table-59
    Crown-34
    Pavilion-40.8

    It comes out to a 1.5, but no red tones.
     
  10. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    [​IMG]
     
    


    


  11. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    That is the table size affecting the ' red tones' theoretically, if for example you enter the same specs but change the table % to 56% you will see more in the red zone in the chart where it lands. A diamond with a slightly larger table could also have a different look to it, albeit subtle - it is possible you could notice a little less fire. But as above the HCA is not used for selection but elimination, the best way to find out more about any particular diamond is to ask the vendor if it is in house for a good description of its personality, and images.
     
  12. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    so, would you think the specs for the above diamond are worthy of a closer look? Or does diamond B make it no contest?
     
  13. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    Yes I think it is definitely worth a closer look, I prefer B as the table is smaller but our new A appears to be well cut and worthy of being on the short list for further evaluation.
     
  14. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    I''d say both are worthy of a closer look. IS &/or ASET images will help a lot, as will pictures.

    I''m guessing from the numbers that these are both GIA graded stones. Since GIA rounds the numbers, which way they are rounded can make a difference in whether the stone is a very good performer or an outstanding one. The "B" stone is a safer pick if you had to go without images, but if the vendor can supply images, that would help greatly.
     
  15. HornAround
    Shiny_Rock

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  16. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    too many inclusions?
     
  17. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    Doesn''t look like it but anyway the only way to tell is to ask the vendor. The diamond looks good.
     
  18. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    inclusions aren''t an issue. You can really only see them because of the level of magnification, at normal size, I''d bet it''s eye clean.

    Ask James Allen for IdealScope images on this one.
     
  19. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    I see a spec on the mid left side. Will that be noticeable to the naked eye?
     
  20. Lorelei
    Super_Ideal_Rock

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    by Lorelei » Apr 23, 2009
    I can''t tell you that, the only way to know is to get the vendor to inspect the diamond for you and let you know. Remember these images are greatly magnified and we are discussing something that is in reality around the size of a pencil eraser!
     
  21. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    Talked to the rep and he says pretty much every VS2 is going to be eye clean. I requested an Idealscope and a verification of it being eye clean. Anything else I should do?
     
  22. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    Definitely ask, but here is another visual. And this is still a bit larger than the actual stone--depending on your monitor resolution.

    83no2.JPG
     
  23. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    that pic is too small. It says the Fluorescence is faint. Should I worry about that?
     
  24. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    Also, the cut concerns me as it only is premium.
     
  25. jet2ks
    Ideal_Rock

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    by jet2ks » Apr 23, 2009
    Can you link the actual diamond? If you have requested an IdealScope image, JA will hold the stone for 24hours after the image is made and sent to you. If you could post a link, it would let people get a better idea of the stone, and since it will be on hold, you don''t have to worry about a lurker poaching it.
     
  26. HornAround
    Shiny_Rock

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  27. Stone-cold11
    Super_Ideal_Rock

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    by Stone-cold11 » Apr 23, 2009
    Nothing to worry about a faint fluor. You will not notice it.
     
  28. HornAround
    Shiny_Rock

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    by HornAround » Apr 23, 2009
    the dimensions worry me a bit too.


    5.94 x 6.15 x 3.70

    compared too a

    6.11 x 6.05 x 3.72 mm
     
  29. Stone-cold11
    Super_Ideal_Rock

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    by Stone-cold11 » Apr 23, 2009
    This is to show what your diamond would look like in actual size. Do you think you can see the inclusion with a diamond this size? Stop worrying about the inclusions.
     
  30. Stone-cold11
    Super_Ideal_Rock

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    by Stone-cold11 » Apr 23, 2009
    Why are you worrying about the dimensions? What are the weight difference?
     
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