polish and symmetry

[paulp]

What is the real difference between very good and excellent when it comes to polish & sym.....??

What about the very good vs. excellent when it comes to cut??

I''ve been trying to get excellents for all 3, Is there an area where I can compromise??

My budget is $3500 +/- , I''m thinking going as high as H in color and VS2 or better clarity and shopping for something in
the .90 range.

Thanks!!

 

[Lorelei]

Date: 11/13/2009 8:43:25 AM
Author:paulp
What is the real difference between very good and excellent when it comes to polish & sym.....?? Really no visible difference to the naked untrained eye. Read more here, polish and symmetry

What about the very good vs. excellent when it comes to cut?? This one is a difficult, don't go by cut labels such as Very Good or Excellent as absolute guarantees of a certain level of cut quality as this can be misleading. Also some VG's can be superb diamonds and conversely some Excellent may not be, so evaluate each diamond on its own desirable physical and visual properties in each and every case.

I've been trying to get excellents for all 3, Is there an area where I can compromise?? It depends on the diamond. As above some Excellent cut grades might not have the best proportions. Generally look for GIA Excellent that score below 2 on the cut advisor in the first instance, you might find with a well proportioned diamond that you can lower polish and symmetry without visual sacrifice.

My budget is $3500 +/- , I'm thinking going as high as H in color and VS2 or better clarity and shopping for something in
the .90 range.

Thanks!!

 

[paulp]

I guess I should have asked (not pertaining to the naked eye) will one effect performance over the other as far as polish and symm??

I will look at some other cut grades and see what happens.......

 

[jet2ks]

Date: 11/13/2009 9:07:16 AM
Author: paulp
I guess I should have asked (not pertaining to the naked eye) will one effect performance over the other as far as polish and symm??

I will look at some other cut grades and see what happens.......

If you stay VG and above on polish and symmetry, there will be no issues. The naked eye just cannot distinguish the difference, so one does not affect performance over the other in this case. Much more important is that the angles compliment each other to reflect light around well.

 

[tyty333]

Here is a nice G/SI1 in your price range...only .85 though...$3420
http://www.whiteflash.com/round/Round-cut-diamond-2219643.htm

Edit ---
$3780 .9 G SI1
http://www.jamesallen.com/diamonds/G-SI1-Ideal-Cut-Round-Diamond-1256306.asp

I'm having a tough time finding ones that meet your specs and still in your price range.
Could you drop down to an I in color and eye-clean SI1 or would you rather go down
in size (or possibly up your budget)? Or are you buying locally and there is no reason
to be looking for stones?

 

[Lorelei]

Date: 11/13/2009 9:07:16 AM
Author: paulp
I guess I should have asked (not pertaining to the naked eye) will one effect performance over the other as far as polish and symm??

I will look at some other cut grades and see what happens.......

No. These are details of finish, more important are the overall proportions and critical angles as Jet points out.

 

[stone-cold11]

This 2? Ask JA for Idealscope image if interested.

http://www.jamesallen.com/diamonds/H-VS1-Ideal-Cut-Round-Diamond-1269088.asp

http://www.jamesallen.com/diamonds/H-VS2-Ideal-Cut-Round-Diamond-1260140.asp

 

[Allium]

Very good on either/both is absolutely fine. Truthfully, excellent polish is overkill and totally unnecessary.

 

[Rockdiamond]

Date: 11/13/2009 9:12:53 AM
Author: jet2ks

Date: 11/13/2009 9:07:16 AM
Author: paulp
I guess I should have asked (not pertaining to the naked eye) will one effect performance over the other as far as polish and symm??

I will look at some other cut grades and see what happens.......

If you stay VG and above on polish and symmetry, there will be no issues. The naked eye just cannot distinguish the difference, so one does not affect performance over the other in this case. Much more important is that the angles compliment each other to reflect light around well.

I agree- but I'd even go a bit further.
In my experience, it's not possible to see the difference between "Good" and "EX" on the polish grade naked eye- and even can be extremely difficult with a loupe.

Symmetry of "good" may be more easily seen than Polish- but unless you're looking for H&A type symmetry, that may also not be an issue.
That said, today with more efficient tools and better cutters most of the round stones you'll find online will be VG or better.

Lorelie gave what I consder to be great advice- especially in your price range.
Consider stones of VG cut grade.

 

[FB.]

Excellent polish is barely noticeable. Excellent symmetry is more noticeable but not essential.

I generally insist on at least very good polish - I regard "good" or lower levels of polish to be a possible sign that the cutter hasn't produced a stone that he was proud of. Excellent polish adds a bit to the cost but adds nothing to what I can see with the naked eye, when compared to very good polish.

Excellent symmetry is nice in rounds, although very good is often adequate. Better symmetry can help borderline cut grade stones to perform better.
Very good symmetry is about the best you'll usually find in pears, cushions and many other fancy shapes and as a result, I'll sometimes drop down to "good" symmetry for the right stone.

H, VS2, 0.9ct sounds a sensible combination, if well-cut.
It'll look almost like a 1ct stone, will be eye clean and have a barely noticeable tint in most light conditions.
You might be able to drop to SI1 clarity (but ask the seller if it's eye clean - the majority of SI1 will be) and the saving of money might allow stepping up to G colour or very close to 1ct.

 

[jet2ks]

Date: 11/13/2009 2:44:18 PM
Author: Rockdiamond

Date: 11/13/2009 9:12:53 AM
Author: jet2ks

Date: 11/13/2009 9:07:16 AM
Author: paulp
I guess I should have asked (not pertaining to the naked eye) will one effect performance over the other as far as polish and symm??

I will look at some other cut grades and see what happens.......

If you stay VG and above on polish and symmetry, there will be no issues. The naked eye just cannot distinguish the difference, so one does not affect performance over the other in this case. Much more important is that the angles compliment each other to reflect light around well.

I agree- but I'd even go a bit further.
In my experience, it's not possible to see the difference between 'Good' and 'EX' on the polish grade naked eye- and even can be extremely difficult with a loupe.

Symmetry of 'good' may be more easily seen than Polish- but unless you're looking for H&A type symmetry, that may also not be an issue.
That said, today with more efficient tools and better cutters most of the round stones you'll find online will be VG or better.

Lorelie gave what I consder to be great advice- especially in your price range.
Consider stones of VG cut grade.

Don't have a heart attack, David, but I agree completely with this. The reason I say VG or better is because of the reason you point out. There are so many diamonds out there that have VG or Ex polish and symmetry, it is relatively easy to find one and have more peace of mind with the purchase. As FB points out, it is a sign that the cutter took a little more care and pride in their work.

 

[Rockdiamond]

jet- I'll bet if we sat down over a beer and some diamonds we'd find a lot of common ground!

As FB points out, it is a sign that the cutter took a little more care and pride in their work.

The above statement sounds like it should make perfect sense.
However in the real world, sometimes "good" polish is left for other reasons.
Cutters need to make a lot of decisions.
For example: say the one facet causing the downgrade to "good" polish is not visible from the top, and positioned so that "fixing" it would require polishing away a lot of the stone to keep it symmetrical.

This type of thing is far more common in Fancy Shapes.
For this reason I do not automatically assume a stone of "good" polish was left that way due to a lack of desire or ability to produce the best stone.

 

[FB.]

David

Yes, in some cases, the cutter had no choice but to leave a less-well-polished surface or risk spoiling an otherwise excellent stone.
But the majority of round stones that I've seen with only "good" polish only rarely manage to attain GIA Very good or Excellent cut.

 

[jet2ks]

Date: 11/13/2009 3:38:51 PM
Author: Rockdiamond
jet- I''ll bet if we sat down over a beer and some diamonds we''d find a lot of common ground!

As FB points out, it is a sign that the cutter took a little more care and pride in their work.

The above statement sounds like it should make perfect sense.
However in the real world, sometimes ''good'' polish is left for other reasons.
Cutters need to make a lot of decisions.
For example: say the one facet causing the downgrade to ''good'' polish is not visible from the top, and positioned so that ''fixing'' it would require polishing away a lot of the stone to keep it symmetrical.

This type of thing is far more common in Fancy Shapes.
For this reason I do not automatically assume a stone of ''good'' polish was left that way due to a lack of desire or ability to produce the best stone.

Yep, I''ve seen some beautiful fancies that had "good" symmetry, as well. I wouldn''t automatically dismiss such a diamond, especially if it was a difficult to find combination of size/color/clarity/shape, but in a round of this size, they are common enough to find one that is "mind clean"

 

[paulp]

Thanks for the advice...

Next question, how heavily can I rely on the HCA? How good of an indicator is it, I understand its only a tool but??? I found a stone that scores a .7, waiting for eye clean verification....

 

[stone-cold11]

Quite accurate, generally under 2 will not show leakage in the Idealscope image, but also depends on how the numbers are averaged and rounded.

 

[FB.]

HCA is quite good, but it is not able to consider the minor facet data, nor any minor tweaks that cutters have made to the basic facet alignment.
Excellent symmetry is also not considered by HCA, but symmetry can make a difference.

The best stones score between 1-2. The next best stones score between 0-1 or 2-3.

HCA can only help to screen out potential bad stones. It can't tell for sure whether a stone is really as good as it seems "on paper", since, as I said, minor facet details, symmetry and cutters tricks can affect how the stone will really look.
Having said that; if you have a GIA-Excellent cut, with excellent symmetry, that scores below 3 on HCA, it's not likely to have many issues because the GIA would penalise the stone to Very good cut if the cutter was naughty. But not all GIA Excellent cuts will score well on HCA and you need to see them for real before commiting.
But GIA very good cut and lower can include cutters nasty tricks that make the stone much different to HCA's prediction.

 

[stone-cold11]

Note, GIA lab symm is not the same as optical symm. Optical symm is what can improve the overall light performance of the stone with a HCA score of 2-3, lab symm not necessary.

 

[paulp]

Date: 11/13/2009 5:36:36 PM
Author: FB.
HCA is quite good, but it is not able to consider the minor facet data, nor any minor tweaks that cutters have made to the basic facet alignment.
Excellent symmetry is also not considered by HCA, but symmetry can make a difference.

The best stones score between 1-2. The next best stones score between 0-1 or 2-3.

HCA can only help to screen out potential bad stones. It can''t tell for sure whether a stone is really as good as it seems ''on paper'', since, as I said, minor facet details, symmetry and cutters tricks can affect how the stone will really look.
Having said that; if you have a GIA-Excellent cut, with excellent symmetry, that scores below 3 on HCA, it''s not likely to have many issues because the GIA would penalise the stone to Very good cut if the cutter was naughty. But not all GIA Excellent cuts will score well on HCA and you need to see them for real before commiting.
But GIA very good cut and lower can include cutters nasty tricks that make the stone much different to HCA''s prediction.

I thought closest to Zero is best.. Am I wrong??

 

[stone-cold11]

Not necessary, lower score is not necessary better, HCA is just a rejection tool. Lower score usually has more obstruction issue, but not that much, you just have to check it and make sure if it is there it does not bother you.

 

[Lorelei]

Date: 11/13/2009 5:28:53 PM
Author: paulp
Thanks for the advice...

Next question, how heavily can I rely on the HCA? How good of an indicator is it, I understand its only a tool but??? I found a stone that scores a .7, waiting for eye clean verification....

The HCA is used for rejection not selection. The aim is to see which diamonds score below 2 then evaluate from there with Idealscope images etc. Often diamonds scoring between 1 and 2 can be good contenders for ring stones, diamonds which score between 2 and 3 can sometimes work if they have top symmetry.

Diamonds which score below 1 can need careful checking for obstruction issues in some cases, this is where the stone visibly darkens at close scrutiny due to head shadow.

 

[paulp]

Date: 11/14/2009 6:38:33 AM
Author: Lorelei

Date: 11/13/2009 5:28:53 PM
Author: paulp
Thanks for the advice...

Next question, how heavily can I rely on the HCA? How good of an indicator is it, I understand its only a tool but??? I found a stone that scores a .7, waiting for eye clean verification....

The HCA is used for rejection not selection. The aim is to see which diamonds score below 2 then evaluate from there with Idealscope images etc. Often diamonds scoring between 1 and 2 can be good contenders for ring stones, diamonds which score between 2 and 3 can sometimes work if they have top symmetry.

Diamonds which score below 1 can need careful checking for obstruction issues in some cases, this is where the stone visibly darkens at close scrutiny due to head shadow.

Thanks to all for your great help. I was thinking closer to zero meant the stone would perform better because the HCA showed my .7 to be "excellent" in all categories rather than when its say a 1.2 it will have some "very good" scores??. I will use the 1-2 range for keepers and rule others out.

 

[Lorelei]

Date: 11/14/2009 8:13:35 AM
Author: paulp

Date: 11/14/2009 6:38:33 AM
Author: Lorelei

Date: 11/13/2009 5:28:53 PM
Author: paulp
Thanks for the advice...

Next question, how heavily can I rely on the HCA? How good of an indicator is it, I understand its only a tool but??? I found a stone that scores a .7, waiting for eye clean verification....

The HCA is used for rejection not selection. The aim is to see which diamonds score below 2 then evaluate from there with Idealscope images etc. Often diamonds scoring between 1 and 2 can be good contenders for ring stones, diamonds which score between 2 and 3 can sometimes work if they have top symmetry.

Diamonds which score below 1 can need careful checking for obstruction issues in some cases, this is where the stone visibly darkens at close scrutiny due to head shadow.

Thanks to all for your great help. I was thinking closer to zero meant the stone would perform better because the HCA showed my .7 to be 'excellent' in all categories rather than when its say a 1.2 it will have some 'very good' scores??. I will use the 1-2 range for keepers and rule others out.

You are most welcome! What sometimes happens with the below 1 scorers is that these can get Ex in all categories as they are sometimes shallower proportioned with shallow depths in some cases. Most top cut diamonds get only VG for spread on the HCA unless the depths are less than 60.3% thereabouts, this is normal. You can focus on 1 - 2 scorers but just be aware that some stones especially if not of top cut quality which score below 1 might possibly show obstruction issues and need checking accordingly.

 

[stone-cold11]

No need to rule 0-1 out, just need to be checked out with an IS for obstruction issue. CraftedbyInfinity stones are usually in that range and they are great performers.

 

[FB.]

It''s also worth noting that GIA round crown angles into 0.5'' increments and pavilion angles into 0.2'' increments.
Therefore, it is possible that the true crown and pavilion angles are slightly rounded-off. In any case, the angles will vary very slightly as you go round the stone.
If you want to be really picky, bear that in mind - as well as the positive benefit of better symmetry.

 

[outatouch0]

Great advice given here.
Only thing I would add - given your budget which was the same as mine - keep in mind when it comes to size (vs. cut quality) we are talking about less than a MILLIMETER. The visual difference between 0.75ct and 0.9ct is difficult to detect (for most people) unless side by side.
I struggled with the size issue until I grasped this concept. The ring in my sig scored 0.7-0.8 on HCA and is a 0.73ct. The light performance is the first thing anyone notices and no one has yet to ask, "How many cts?" and I/we have no regrets on the stone or ring.