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Is the HCA reading important


confused888
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I am in the market for a diamond for my girlfriends engagement ring. I have been trying to learn as much as possible about diamonds on the web for about 2 months now, but I am still really confused about what is important and what is not. It all seems so complicated and all the websites seem to contradict each other.

 

I have finally found a diamond which I think is nice but having got the sarin report and put the numbers through the HCA it does not perform very well. Is it important for the HCA reading to be good?

 

I am told it is an Ideal cut diamond with Polish/Symmetry: EX/EX, but if so why does it score so badly on the HCA?

 

The sarin report is as follows:

 

Weight 2.03 Ct.

Diameter(mm) 8.13 (8.08-8.18) [1.2%]

Total Depth 61.9% 5.03mm

Crown Angle 35.5' (35.2-35.8) 0

Crown Height 14.9% (14.3-15.5)

Pavil Angle 41.2' (40.8-42.2) 0

Pavil Depth 43.7% (43.3-44.7) 0

Culet 0.6% V.Small 0

Table Size 55.1% (54.8-55.5) 0

Girdle Thickness 1.6% (1.1-2.1) Medium 0

Proportion 0

 

Thanks for your help.

 

P.S. These forums are so helpful for clueless people like me?

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confused888,

 

The HCA is a tool that many people feel can be a good indicator of a diamonds overall performance. I think the program has merit, but at the same time I agree with some of the critics that the HCA has limits. There is a vocal minority that think the HCA is completely worthless, although I don't personally find that to tbe the case whatsoever.

 

The diamond you selected received a poor HCA score because the average pavillion angle is 41.2 degrees. HCA really punishes diamonds that have pavillion angles over the 41 mark, especially if the crown angle is also on the steep side (as is this diamond at 35.5).

 

Regardless of HCA, the particular diamond you're considering does have a "steep/deep" set of proportions. That means that although the stone is AGS "Ideal", it is not the "best" of the ideal proportions. Furthermore I would bet if you looked at that diamond using an Idealscope (or other red reflector) you would see a ring of light leakage around the table.

 

At the end of the day, however, what I think the HCA and other tools fail to evaluate or report is the SIGNIFICANCE of the light leakage. The diamond leaks some light around the table - so what? Does that mean the stone isn't beautiful? Does that mean it isn't a good value? Does that mean it isn't something you should buy? It is the INTERPRETATION of HCA, Idealscope images, BS reports etc that IMO is most confusing - not the reports, scores or images themselves.

 

I would suggest you try and see if you can find a diamond that scores better on the HCA, then compare the two side by side. If that is not possible you might be able to contract the services of an appraiser and have them do the comparison for you. If all else fails, buy the diamond and do your own comparison to local stones. My bet is that you'll find the diamond to be absolutely breathtaking and beautiful, just like tens of thousands of people who bought similar diamonds long before HCA was ever invented :)

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The HCA according to it's author is a rejection tool not a pick tool . It has limited utility in enabling a consumer to discard the chaff.

 

Keep in mind that it measures only the average of 17 of the 58 facets that comprise the round brilliant shape and does not factor in the alignment of the facets that are responsible for maximizing light performance.

 

Excelllent Polish and Excellent Symmetry speak to the external configuration of the diamond but tells you nothing regarding the facet alignment responsible for it's light performance.

 

I've attached a graphic of a GIA Excellent/Excellent Ideal Cut diamond. Note it's HCA score which falls into the Excellent category on the HCA scale but demonstrates mediocre light performance as measured by the Brilliancescope.

post-2-1130887987.jpg

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