HCA 1.7 H&A 2 Carat Diamond

[HDer]

https://www.jamesallen.com/loose-di...rat-k-color-vvs1-clarity-good-cut-sku-2880697

But IGI good?

I wonder what this would look like in real life. The face up view looks a lot better than most in the video. Obviously super deep.

 

[Dancing Fire]

Nothing good about this stone... a well cut 2ct should be closer to 8.1mm. 64.1% depth with thick girdle..

 

[rockysalamander]

IGI Mumbai is not a reliable grader for color or clarity. But, for discussion as I think this is a theoretical question for your, lets make the assumption that they can accurately measure angles.

The question to me is are the angles complimentary for a 64.1% depth stone (crown 38.40, pavilion 39.70)? On the 64% AGS table, this combination would get a Good.

But, you don't need HCA or AGS to tell you that this is a deep stone cut for weight retention. You can see the dark center, almost like a nail-head visible in the video. When paired with the thick girdle, it means there is a lot of depth in the belly -- i.e., you are paying for depth you don't get in spread. That diamond should be closer to 8 mm in size, and this one is 7.8.

IRL, I think it will have a lot of contrast at certain angles of viewing. The edges will have some life and provide a lot of the sparkle and scintillation for this stone -- but the center will be persistently flat. With a stone of this size and with a 57% table, the depth is especially apparent.

I don't have DiamonCalc, but I think if someone runs these numbers you will see a very grey/leaky area under the table with additional leakage along the girdle facets.

 

[flyingpig]

First, 2.0c should be well above 8.00mm (in some cases 8.10mm+). You only get 7.8xmm
Second, it is very leaky and dead under the table between arrow shafts in 10 and 11 o clock areas

leaky table, persistent obstruction. it will be a relatively dark/dull stone in real life from a normal viewing distance (for a ring)
not a good performer, terrible spread, not the most respected lab

Such steep and shallow combo can look ok with little leakage.
Something like this is more promising.
https://www.jamesallen.com/loose-di...-color-vvs2-clarity-very-good-cut-sku-3042656

There is a recent discussion.
https://www.pricescope.com/communit...-still-good-or-not.233971/page-2#post-4209480

 

[HDer]

Thanks guys. Wasn't seriously considering buying this stone. Just thought it was interesting that a stone with a low HCA and decent looking face up view could have such a low cut score.

 

[flyingpig]

Thanks guys. Wasn't seriously considering buying this stone. Just thought it was interesting that a stone with a low HCA and decent looking face up view could have such a low cut score.

Both GIA and AGS cut grade systems consider spread and durability, in addition to appearance. AGS goes further and breaks down light performance into four sub categories (leakage, contrast, brightness and dispersion). This paricular stone may have gotten significant deductions in leakage, contrast and spread.

Therefore, the general and logical recommendation is to stick with GIA ex or AGS ideal/ex, unless the buyer understands what he/she is doing.

Most new members cannot digest all this nerdy information anyways, so often we simply say "too deep, look for GIA ex or AGS ideal"

 

[valeria101]

leakage, contrast and spread

Leakage & contrast should be caught by the HCA ... Spread too, with some factor.

+

The deep cut might play up colour - a detail beyond the HCA. Interesting enough in a light brownish yellow RBC esp. since colour grading rules may not account for optical effects in this range [detail to check; much more interesting at the W-X / Fancy Light borderline, of course !]

Don't know if there ever was any intention to account for this effect in the HCA; it does seem possible.

2c

 

[flyingpig]

HCA may catch leakage, but not necessarily persistent contrast or obstruction. This is according to Garry's video.

 

[valeria101]

HCA may catch leakage, but not necessarily persistent contrast or obstruction. This is according to Garry's video.

I am not seeing egregious contrast in the video: no reflecting areas except the arrow pattern. The stone is tilted a bit, so I am letting some approximation for faint darker/lighter variations appearing in exactly half the stone (darkish upper half).

... Leakage seems too difficult to guesstimate in the 360° lighting situation - tempting as it is to try !

-
Do not remember Garry's comments ... will look them up again. Off the cuff: I am thinking that the contrast etc. missed by the HCA is from painting/digging, which modify the pattern not just its intensity (so if either was the case, we'd see more even in a video that shows the contrast pattern).