QUOTE(204 @ Jul 10 2017, 04:46 PM)
Nice. Thanks for the explanation, i'll be sure to go back to the store to check again. I remember last saw it was at least something like 'very good' in 
However something baffles me, while the Enchanted Cut Score is 96.6% seems to be quite good. But the HCA shows
Selected: 62.5% depth, 58% table, 35.5° crown angle, 41° pavilion angle,
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.
Factor Grade
Light Return Good
Fire Good
Scintillation Good
Spread or diameter for weight Very Good
Total Visual Performance 4.1 - Good - Only if price is your main criterion
Scores of 0-1 are often good for earrings and pendants, but usually not as good for rings. Most people prefer stones that score 1-2 or even top Hearts & Arrows symmetry stones up to 3.0. Zero is almost impossible since many performance factors conflict.
and i remember seeing in this thread that lower is better. Is 4.1 horrible?
First of all, both Enchanted Cut Score and HCA follows a proprietary set of calculations that belongs to each of them individually. Secondly, HCA takes into account 17 facets of a round brilliant only. Standard round brilliant is 57 facets. So, are there still reliable? I would say yes, but as a guideline.
However something baffles me, while the Enchanted Cut Score is 96.6% seems to be quite good. But the HCA shows
Selected: 62.5% depth, 58% table, 35.5° crown angle, 41° pavilion angle,
The result is for a symmetrical diamond with a medium girdle and very good polish
HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003.
Factor Grade
Light Return Good
Fire Good
Scintillation Good
Spread or diameter for weight Very Good
Total Visual Performance 4.1 - Good - Only if price is your main criterion
Scores of 0-1 are often good for earrings and pendants, but usually not as good for rings. Most people prefer stones that score 1-2 or even top Hearts & Arrows symmetry stones up to 3.0. Zero is almost impossible since many performance factors conflict.
and i remember seeing in this thread that lower is better. Is 4.1 horrible?
So what's wrong with the diamond at Wah Chan? Apparently HCA does not like the steep crown angle of 35.5 degree. Initially, I tried to reduce the depth of 62.5% to 61.5%. Score only improved by 0.1. However, when I tried to reduce the crown angle to 35, while remain the other values as per cert and the score improved to 2.5! So apparently HCA is somewhat telling us that the crown angle is too steep. Feel free to play with other numbers as well, like the pavilion angle, try to lower it below 41 degree and see.
Update:
I have read online regarding 35.5 degrees from other blogger and it seems that it is the maximum he would go. I have also checked with Todd Gray from www.niceice.com before and he said that the only way he can aceept a 35.5 crown angle was that the crown height is not deeper than 15.5% (The GIA diamond you posted has 15%) and the depth cannot be more than 43.3% if the pavilion angle is 41 degrees. So I am sorry that I said that this diamond is acceptable.
QUOTE
The problem with 41.0 degrees is that it really only works if the pavilion depth is 43.3% or lower. A pavilion depth of 43.5% is the kiss of death, it's known as the critical tipping point where light begins not to strike fully off the pavilion facets.
Anyway, I would still suggest you to take a look at the diamond using H&A scope first at Wah Chan. This is to better equip yourself with more knowledge before purchasing.
If you want proven numbers, cut quality, and light return, you may take a look at the diamond I posted earlier. That is a pretty good Hearts & Arrows diamond. Try to pluck in the numbers into HCA and it should be below 2.
This post has been edited by kambingkoh: Jul 10 2017, 05:14 PM
Jul 10 2017, 05:08 PM

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