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newbs

Rough_Rock
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Hello all. This is a fantastic site. I''ve been lurking for a while - trying to educatate myself as much as I can. We''re looking at upgrading my .75 RB to possibly 1.25. I''ve discovered the HCA chart. I''m confused....why are some diamonds rated excellent/Ideal cut, but then when we put the numbers through the chart they don''t score well?

Thanks!
 

Stone-cold11

Super_Ideal_Rock
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Common, because GIA Ex cut grade allows for crown and pavilion angle combiinations that has less than optimal light performance. Else we could easily depend on GIA grade and forget about using the HCA.
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 9:24:02 AM
Author:newbs
Hello all. This is a fantastic site. I've been lurking for a while - trying to educatate myself as much as I can. We're looking at upgrading my .75 RB to possibly 1.25. I've discovered the HCA chart. I'm confused....why are some diamonds rated excellent/Ideal cut, but then when we put the numbers through the chart they don't score well?

Thanks!
Because GIA 's Excellent cut criteria is broad and can allow for less desirable angle combos to get the ex cut grade. Also be cautious of so called Ideal Cut, Premium Cut labels when used by vendors, these are no guarantee of a well cut diamond. Also remember the HCA is used as a first round elimination tool, it isn't used for selection. It is always best to carefully evaluate each diamond on its own desirable visual and physical properties regardless of cut grade.
 

newbs

Rough_Rock
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One of the diamonds we''re looking at is graded as VG cut, but scores .8 on the HCA - whereas another is graded Excellent/Ideal, and scores 4.7. The jeweller we''re dealing with doesn''t use the HCA and insists that if it''s graded an excellent/Ideal cut, then you''re getting an excellent cut diamond.
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 9:51:56 AM
Author: newbs
One of the diamonds we're looking at is graded as VG cut, but scores .8 on the HCA - whereas another is graded Excellent/Ideal, and scores 4.7. The jeweller we're dealing with doesn't use the HCA and insists that if it's graded an excellent/Ideal cut, then you're getting an excellent cut diamond.
It could be the second diamond has steep deep angles which accounts for the poor HCA score. Your jeweller is unfortunately misinformed that if a diamond is graded as Excellent or Ideal cut that it is automatically a well cut diamond. This is not the case. The only meaningful use of the term Ideal Cut pertains to AGS0 Ideal Cut grade which for the most part should get you a well cut diamond, otherwise proceed with extreme caution.

If you could post the proportions of each then that would be helpful but suffice to say I would pass on the second diamond even without more info as the chances are it is not well cut. If you could post all the proportions on the first VG cut then I can probably see why the diamond was awarded VG, see if there are any comments on the report also such as cut grade affected by brillianteering, but we need the depth, table, angles, girdle - all the info on the report please.
 

Stone-cold11

Super_Ideal_Rock
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Date: 3/16/2009 9:51:56 AM
Author: newbs
One of the diamonds we''re looking at is graded as VG cut, but scores .8 on the HCA - whereas another is graded Excellent/Ideal, and scores 4.7. The jeweller we''re dealing with doesn''t use the HCA and insists that if it''s graded an excellent/Ideal cut, then you''re getting an excellent cut diamond.
Give us the numbers for the first stone, and we will try and tell you why it is graded VG by GIA and why HCA prefers it.
 

oldminer

Ideal_Rock
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The problem is not so much with the systems in place at GIA, or AGS. It is also not so much a problem of the HCA. Diamonds are each individuals although we can make somewhat broad categories for them to assist people. We often end up creating confusion such as you are experiencing. Ultimately most Excellent cut GIA diamonds really do look very beautiful and will please nearly everyone. A person who gets and AGS 000 stone will undoubtedly think the diamond is lovely to look at, too. People who get a diamond with an HCA score as low as .8 certainly won't have a problem with the looks of their diamond. Each one of these system has variation of appearance, but they all are rather minor ones at the top category.

What we really can't agree upon, as an industry, is what "fine cut" really means. It currently means many different things to those of us who are involved. We more or less agree on some points, but market forces, competition and the fact that no governmental agency is in charge, stand in the way of clearly defining "fine cut" in diamonds. The sort of slight differences among diamonds at the top range of well cut are the kind of differences important to engineers, scientists and avid diamond fanatics, but of a lot less importance to romantics and appreciators of beauty. We just are not quite at the scientific level of grading we are striving to attain, but we sure know how to make pretty diamonds for many years already. Turning diamond grading into a science is swtrongly apposed by traditionalists of the diamond business. Many of these people and firms are hugely strong and financially powerful. What they don't want to happen generally does not happen. They apply pressure to the major labs to keep the status quo as it suits their traditional model. Since they are the primary clients of the labs, their financial clout is evident. Progress toward science based grading has been very slow, but it is not stagnant entirely.

Pricescope has become a huge force of change. Consumers, armed with facts, now pursue the diamonds they are looking for with power nearly matching the traditionalists. As the demographic of savvy consumers grows larger, you will see more labs converging on scientifically provable grading strategies. I see no possible outcome other than this, but I can't say when.

Try to find what it is about a diamond which you consider its beauty. Consider the cut grade as a part of the process since a well cut diamond is not only beautiful, but may be less damage prone than a less well cut diamond. A well cut diamond ought to look size appropriate for its weight, and not small for the weight. All of these considerations are part of what makes a fine diamond.

I hope you become less worried and also less confused.
 

newbs

Rough_Rock
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these are the 2:

RB 1.21
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 57%
Depth: 62.7%
Crown: 35.5
Pavillion: 41.0

RB 1.23
Color: G
Clairy: SI 1
Cut Grade: VG
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 58%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.4
 

Stone-cold11

Super_Ideal_Rock
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Date: 3/16/2009 11:48:17 AM
Author: newbs
these are the 2:

RB 1.21
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 57%
Depth: 62.7%
Crown: 35.5
Pavillion: 41.0

RB 1.23
Color: G
Clairy: SI 1
Cut Grade: VG
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 58%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.4
Under the new GIA guidelines, the 1.21 F SI1 should be graded as a VG in cut because of it''s depth, new cut-off is at 62.3%.

The 1.23 G SI1 is outside of GIA Ex cut in the Pav angle for that table and crown angle. But it falls in the AGS0 cut performance, it should perform better than the 1.21 F SI1 stone optically and in spread.
 

newbs

Rough_Rock
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Thank you for your responses. This is so confusing. How about this one....

RB 1.30
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: Excellent
Fluorescence: None
Table: 59%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.8
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 11:48:17 AM
Author: newbs
these are the 2:

RB 1.21
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 57%
Depth: 62.7%
Crown: 35.5
Pavillion: 41.0

RB 1.23
Color: G
Clairy: SI 1
Cut Grade: VG
Polish: VG
Symmetry: VG
Fluorescence: None
Table: 58%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.4
The first got VG because of the depth and is also a steep angled combo as I originally estimated, the second because of the shallower pavilion angle. From the info we have I would be most interested in the second diamond out of the two, but I would like to see an ASET or Idealscope image for this diamond due to the shallow pavilion angle, do you have the girdle thicknesses too please?
 

Stone-cold11

Super_Ideal_Rock
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Date: 3/16/2009 12:17:04 PM
Author: newbs
Thank you for your responses. This is so confusing. How about this one....

RB 1.30
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: Excellent
Fluorescence: None
Table: 59%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.8
Not that great, borderline case for the HCA, light performance will depends on other facets and optical symmetry, could be good or bad but no way to know from just the numbers. We will need IS/ASET images for this.

Still prefers the 1.23 G SI1.
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 12:17:04 PM
Author: newbs
Thank you for your responses. This is so confusing. How about this one....

RB 1.30
Color: F
Clairy: SI 1
Cut Grade: Excellent
Polish: VG
Symmetry: Excellent
Fluorescence: None
Table: 59%
Depth: 60.6%
Crown: 35.5
Pavillion: 40.8
This one is hovering around a steeper angled range also, can you get an ASET or Idealscope image for this diamond if it is online - or do I take it you can see these diamonds in person? Don't feel overwhelmed - you are on the right track and I will try to make this as easy as possible for you and try not to overcomplicate things!
 

newbs

Rough_Rock
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the Girdles:

1.21 = slightly thick (faceted)
1.23 = medium (faceted)
1.30 = slightly thick (faceted)
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 12:27:45 PM
Author: newbs
the Girdles:

1.21 = slightly thick (faceted)
1.23 = medium (faceted)
1.30 = slightly thick (faceted)
Those are fine, thanks for posting them!
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 12:30:43 PM
Author: newbs
what does medium faceted mean?
It just means the girdle is considered medium and faceted, this page explains further. Most diamonds have a faceted girdle rather than bruted or other finishes.

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

Girdles are usually described as very thin, extremely thin, thin, medium, slightly thick, thick, ex thick and so on. It is best to look for a girdle which doesn't have too much variation such as thin to medium, thin to slightly thick etc. Avoid extremes such as thin to thick, very thin to thick and suchlike.
 

newbs

Rough_Rock
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My preference is the 1.23 - probably because of the .8 score. Should I be concerned about the SI 1 clarity?
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 12:49:17 PM
Author: newbs
My preference is the 1.23 - probably because of the .8 score. Should I be concerned about the SI 1 clarity?
If you can see the diamond in person check it out away from the store lights to make sure it is eyeclean to your standards and that you like how it looks in everyday lighting. If the diamond is being sold online, you will need to ask the vendor to check it is eyeclean and make your expectations known concerning this. For example, if you don't want to see any inclusions at close scrutiny from any angle, make sure the vendor knows that so you are both on the same page. Also if the diamond is online, ask for an ASET or Idealscope image of the diamond.

Also don't use the HCA to choose a diamond, it isn't used for that purpose but for elimination. A lower score isn't better than a higher one once you score below 2, as I said earlier an ASET or Idealscope image of the diamond would be very useful.
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 12:55:00 PM
Author: newbs
I can''t see the stone...we''re working through email.
In that case you will need to ask the vendor to inspect the diamond for you to see if it is eyeclean or not, and ask for the above images I noted as these would be very helpful. Which vendor are you working with?
 

newbs

Rough_Rock
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He''s a jeweller who was recommened to us by a friend of mine in a different city. We were there a few weeks ago and did see 3 stones - one of which we liked, but when I got home and put the numbers through the HCA, it scored 4.7, so we discarded it. My hubby will be travelling there on business in a few weeks, so he''ll be able to see it then.
I doubt the jeweller will send us pictures. I don''t think he has them....we can always ask. He didn''t know about the HCA.....
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 1:03:54 PM
Author: newbs
He''s a jeweller who was recommened to us by a friend of mine in a different city. We were there a few weeks ago and did see 3 stones - one of which we liked, but when I got home and put the numbers through the HCA, it scored 4.7, so we discarded it. My hubby will be travelling there on business in a few weeks, so he''ll be able to see it then.
I doubt the jeweller will send us pictures. I don''t think he has them....we can always ask. He didn''t know about the HCA.....
Not to worry, you can always do as you have done, post the proportions of any you like and we can advise from there. Get your Hubby to check that diamond out away from the store lights if possible, that will give a good idea of how it will actually look when worn.
 

newbs

Rough_Rock
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I''ll ask him to do that. Thanks again for all your help. This is truly a great forum. Had I not stumbled onto this site, we would have probably gone ahead with the one stone we saw in person. We really don''t know much about diamonds.

How much should a stone like the 1.23 cost us?
 

Stone-cold11

Super_Ideal_Rock
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A well cut 1.21c G SI1 online is priced at 6.3k, so figure about an additional 10-15% markup for a normal store with a shop front is the common practice.
 

Lorelei

Super_Ideal_Rock
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Date: 3/16/2009 3:12:19 PM
Author: newbs
I'll ask him to do that. Thanks again for all your help. This is truly a great forum. Had I not stumbled onto this site, we would have probably gone ahead with the one stone we saw in person. We really don't know much about diamonds.

How much should a stone like the 1.23 cost us?
You can use the search tool Pricescope your Diamond above, this will give prices for online diamonds which are typically cheaper than brick and mortar stores. No real way to tell exact prices as stores can vary so much, but the search tool will give a rough idea if you use that as a lowball figure.

And I am very pleased that I have been of some help to you!
 
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