0.8 vs 1. 3 Holloway numbers, what is the diff?

[alias888]

As quoted from Holloway, "A score below 2 (Excellent) means you have eliminated poor performers... Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5"

So what does that really mean to a lay person? What is the difference between 0.8 and 1.3? Is it visible to the naked eye? What is the difference between Ex and VG in as it relates to scintilation and spread?

Any place with definations for these factors? Haven'' found it yet.

thanks

 

[searcher]

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On 6/24/2004 6:22:54 PM alias888 wrote:






As quoted from Holloway, 'A score below 2 (Excellent) means you have eliminated poor performers... Your own personal preference may be for a diamond with an HCA score of 1.5 more rather than one with a lower score of say 0.5'

So what does that really mean to a lay person? What is the difference between 0.8 and 1.3? Is it visible to the naked eye? What is the difference between Ex and VG in as it relates to scintilation and spread?

Any place with definations for these factors? Haven' found it yet.

thanks
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You won't find it. These diamonds should be regarded as equivalent until you get more information.

 

[Magnum]

The reason for the disclaimer is that the HCA is not an exact tool. It derives it's result from partial information, and thus, there are other factors not taken into account that could affect the beauty of the stone, and make a stone that scores 1.5 more beautiful than one that scores 0.5. the four things it considers are depth percentage, table percentage, average crown angle (of which there are , and average pavilion angle(of which there are also . While it is arguable that these are four very important parts of a diamond's cut, they are not the only parts. The HCA doesn't take into account the variance in those measurements (i.e. how different the 8 pavilion angles are that give you that average measurement), the cutting of the other minor facets, the symmetry of the cutting, etc. So while you may be able to get a good idea of the cut of the diamond with the info you input into the HCA, there are other factors not taken into consideration that could alter the implications of that score. So, a stone that scores 1.5 may have better symmetry, variances, minor facets, etc. than the one that scored 0.5, making it actually more beautiful. That's why people say to use the HCA as a sorting tool, and not a definitive measure of a diamond's beauty. It's not accurate enough to say that a stone that scores 1.1 is better than one that scores 1.2. there is too much margin of error involved. But if you use it to narrow down your search to say, stones that score less than 2, you've narrowed down the chance that you'll find a poorly cut stone in your group. Once you've narrowed down your search to a manageable number, that's when you start looking for more info to help differentiate between the stone.

 

[valeria101]

NONE

Look how THIS stone scored! There is a good reason that the HCA comes with the instruction to consider everything that gets a score above 2 full stop. There is no mention on the respective page that one should focus on smaller differences between two scores...


It seems that you got two worthy candidates just good to separate using a more precise evaluation (done with stone in hand, not by numbers that is) - either by the seller, an appraiser or yourself.