Need Help: GIA Report vs HCA Scoring

[simonho2001sg]

Hi,

Would appreciate if anyone could clear my doubts.
GIA reported triple excellent in Cut, Polish & Symmetry for a 0.56 H & A round brilliant diamond but it has a bad score of 5.6 in HCA.
Why a huge different between the two report? Where has gone wrong?

GIA Report Details are as follows:
Shape and Cutting Style: Round Brilliant
Measurements: 5.32 - 5.35 x 3.22mm
Carat Weight: 0.56 carat
Color Grade: E
Clarity Grade: VVS1
Cut Grade: Excellent
Clarity Charateristics: Pinpoint
Polish: Excellent
Symmetry: Excellent
Fluorescence: None

Proportions:
Depth: 60.4%
Table: 61%
Crown Angle: 34.0%
Crown Height: 13.0%
Pavilion Angle: 41.4%
Pavilion Height: 44.0%
Star length: 55%
Lower half: 75%
Girdle: Medium to Slightly thick, Faceted (3.5%)
Culet: None

Thanks and best regards,
Simon

 

[kenny]

The girdle was placed too high - probably to get the heaviest diamond possible out of that particularly-shapped rough diamond.

When the girdle is where it belongs for optimum light return the diamond will have angles closer to:
Crown Angle 34.7
Pavilion Angle 40.8

This diamond has:
Crown Angle 34.0
Pavilion Angle 41.4

Unfortunately GIA, being friendly with their paymasters (diamond sellers), allows their best Cut grade to include a wider range of proportions than those that yield optimum light return.
Think of a bullseye on a target that is too large so the marksman thinks he's a good shot.

HCA does not depend on income from diamond sellers so it can be more objective and selective, IOW, Honest!

Good cut contributes more the the beauty of a diamond (a spectacular light show) than color or clarity.
I noticed you are looking at E VVS1.
That's wonderful if you realize you are paying much more for what will not be apparent to virtually anyone without a loupe.
If you value high color and clarity due to your taste or perception of purity or appreciation of what is more rare then, fine.
Coincidentally, I knowingly paid for an E VVS1 knowing this because I just wanted it anyway.
Nothing wrong with that for you or for me as long as the decision is made AFTER knowing you can get something that looks similar for much less or get a larger diamond for the same price that's near, say G VS2 or so.

If you want the best light performance in a round there are two steps.
1. HCA under 2.0.
2. Good Idealscope performance. (The angles you input into the HCA are AVERAGES of 16 separate numbers each of which might unfortunately range from high to low but average out just right - this would be revealed by an Idealscope image.

https://www.pricescope.com/tools/ideal-scope

Get IS pics and post them here for feedback or compare them to this chart.
If your vendor won't get you IS pics of the diamond you are considering find a new vendor.