HCA - visible difference between VG and EX

[LikeDeIce]

I have a question regarding the HCA scores. I have two stones:

Stone A
HCA: 1.2, Ex/Ex/Ex/VG
AGS0

Stone B
HCA: 1.7, Ex/VG/VG/VG
AGS0
$500 cheaper than stone A
14 points larger than stone A.


Through my reading here, I''ve read two things. One is that HCA is used as a rejection tool, and can''t determine which of two stones is best if they''re both below the 2.0 mark. The other thing I''ve read is that people prefer stones that are not only below the 2.0 mark, but also score Ex/Ex/Ex/VG.

My Question: Is the difference in fire/scintillation between Ex and VG worth the extra money and the smaller stone? Or, since they both scored below 2.0, should I be leaning toward the bigger, cheaper stone? Thanks in advance!

 

[Lorelei]

Date: 4/7/2008 9:47:06 AM
Author:LikeDeIce
I have a question regarding the HCA scores. I have two stones:

Stone A
HCA: 1.2, Ex/Ex/Ex/VG
AGS0

Stone B
HCA: 1.7, Ex/VG/VG/VG
AGS0
$500 cheaper than stone A
14 points larger than stone A.


Through my reading here, I've read two things. One is that HCA is used as a rejection tool, and can't determine which of two stones is best if they're both below the 2.0 mark. The other thing I've read is that people prefer stones that are not only below the 2.0 mark, but also score Ex/Ex/Ex/VG.

My Question: Is the difference in fire/scintillation between Ex and VG worth the extra money and the smaller stone? Or, since they both scored below 2.0, should I be leaning toward the bigger, cheaper stone? Thanks in advance!

The HCA cannot actually see the diamonds, once you are considering stones such as AGS0, then really the HCA isn't needed. It was originally intended ( to the best of my knowledge) to be a tool to help weed out amongst the many virtual listed diamonds, so that you could knock the lesser performers out of the picture, and concentrate on the ones which were more likely to perform well. It is a very useful tool indeed for doing this, and has been of help to many, but it should not be used to select stones.

Your best bet with the diamonds you are considering, is to ask for Idealscope images or other technologies, and /or ask your vendor which one may best suit your needs, rather than being influenced by something that cannot actually see the diamonds. Also you can post the proportions of each if you like, for further opinions.

I don't know if you have seen this info on HCA, but I thought I would post it anyway.

http://diamonds.pricescope.com/ideal.asp

 

[Regular Guy]

LDI,

My sense, hoping for confirmation from my friends...is that each of your diamonds, by analogy, have passed 2 tests: a) for HCA which is like a hoola hoop, and b) AGS0, which is more like the relative size of a basketball net.

For our near sighted chap, wanting their diamond to pass both tests...having seen it''s passed through the basketball net...he also wants it to pass as close to the center of the hoola hoop (i.e., optimized HCA result) as possible.

Since both are AGS0...I think I''d forget HCA...and look at other criteria...a couple of which you''ve noted, including price & size.

But...others may be able to help more.

Always...you will help yourself by providing more detail, if you can.

Regards,

 

[strmrdr]

post all the numbers from the AGS diagram for both please.

 

[LikeDeIce]

Here are the numbers. One of the stones from my original post was actually snatched up (this was just kinda for my more general knowledge than a specific set of stones), but this is an equally good example.

1.28 I SI2
HCA: 1.7 ex-vg-vg-vg
AGS Grade: 0
Depth: 61.51%
Table: 56.74%
Crown Angle: 34.33°
Pavillion Angle: 40.99°
Girdle: 1.52
Polish: ideal
Symmetry: ideal
Fluor: neg
7.00x6.99x4.30
$6150

1.22 F SI2
HCA: 1.2 ex-ex-ex-vg
AGS Grade: 0, H&A
Depth: 61.5%
Table: 57%
Crown Angle: 34.8°
Pavillion Angle: 40.7°
Girdle: Thin-Medium (faceted)
Polish: ideal
Symmetry: ideal
Fluor: none
6.84-6.87x4.22
$6700

Now I know the 1.22 stone "better" as far as the cut goes, and I know that cut is the most important thing about diamonds, but considering that they are both very, very well cut diamonds, is the slightly better one worth the extra money and reduction in size? I know the size difference of 6 points isn''t that much, but it may be noticeable... while i''m not sure if the difference in cut would be noticeable. What do you think?

 

[LikeDeIce]

To clarify, I guess what I''m asking is the general question of once you get up to the elite-level cut of an AGS0, is there still a noticeable naked-eye difference between the top-end AGS0 and the "average" AGS0?

 

[BlingItOn]

I''m a newbie myself but after 2 upgrades, I''m thinking the $500 you are looking at can probably be attributed to the fact that the smaller stone is an F colour.

No doubt it weighs 0.06cts smaller but we''re also looking at 3 grades higher in the colour scale.
ther than HCA Score, this is the other factor you could probably be looking at in terms of the pricing...Just my $0.02

 

[strmrdr]

both combos are fine by the numbers so far
whats the lgf% which is listed on the V shaped facet on the diagram?

Do you have IS images?

 

[strmrdr]

Date: 4/7/2008 11:59:35 AM
Author: LikeDeIce
To clarify, I guess what I''m asking is the general question of once you get up to the elite-level cut of an AGS0, is there still a noticeable naked-eye difference between the top-end AGS0 and the ''average'' AGS0?

yes, AGS0 doesn''t take h&a into account which can make a difference in the contrast pattern.

 

[LikeDeIce]

Date: 4/7/2008 2:02:10 PM
Author: strmrdr
both combos are fine by the numbers so far
whats the lgf% which is listed on the V shaped facet on the diagram?

Do you have IS images?

I''m not 100% sure if this is what you''re asking for, so if the numbers don''t make any sense, that''s why, but the only other info on the diagram that i didn''t include:

For the 1.22:
1.7% to 3.9%

For the 1.28:
1.1% to 3.2%

as for the IS images, for the 1.22, i''m not sure if the attachment i just put on worked or not, but i tried to attach the pic. The 1.28 stone is here

 

[Ellen]

Those stones will be equally beautiful.

 

[strmrdr]

Date: 4/7/2008 4:18:21 PM
Author: Ellen
Those stones will be equally beautiful.

I agree

hmmm tough choice but I think id go with the I and put the $500+ towards a higher end setting.
Personally I''m fine with I color at that size.

 

[LikeDeIce]

Thanks everyone... what an asset PS has been! I''ve been lurking with an occasional post for 6 months now, and i''m finally closing in on the buy... probably within a couple weeks. Thanks again!

 

[Ellen]

You''re welcome. Let us know which beauty you end up with!